Most general managers don’t overreact after just three weeks of games. But that doesn’t mean they don’t take the first month of performances seriously and start to prepare for potential trades. History tells us not a lot of deals get done at the end of April or beginning of May, but the new generation of GMs is aggressive about making moves, and we’ll see major moves made in May or June, long before the trade deadline at the end of July.

Take the Toronto Blue Jays and the dismal start to their season. You can attribute some of that to having no Edwin Encarnacion, but most of what has gone wrong for them has happened since Opening Day, not as a matter of design. They’ve suffered a barrage of injuries removing two of the best starters (Aaron Sanchez and J.A. Happ) and their best hitter (Josh Donaldson). They’ve gotten horrendous starts from both veterans Jose Bautista and Russell Martin, added to their usual lack of offensive production at first base and left field. Throw in the fact that only one team in the live ball era has started the season 5-13 (the Jays' record through Sunday) and made the postseason -- the 1951 New York Giants -- and you have a strong case for the Toronto front office to walk into the boardroom and start trade talks now.

But in doing that, the Blue Jays really have only three choices:

• Wait it out and hope the team gets healthy and the veteran players start living up to the backs of their baseball cards.

• Trade for upgrades in left field and at first base.

• Start the process of rebuilding.

The problem with the third option is that unless they’re going to consider trading members from their starting rotation (the best part of the team) or Donaldson, they really don’t have much to trade if they’re expecting to get the top prospects they’ll need to really rebuild. They’re probably in the toughest position of any team -- they’re built to win now but they aren’t; they already have holes; and they have injuries that might handicap their getting any kind of deals done that would get them value in return.

In contrast to the Jays' stumbling because of problems that struck them in-season, the San Francisco Giants and Washington Nationals walked into 2017 with glaring needs they were only too aware of.

The Giants desperately needed both an everyday left fielder and a better fourth outfielder to help them deal with the likely absences of injury-prone veterans Hunter Pence and Denard Span. The Giants brought up Christian Arroyo on Monday to play third and will move Eduardo Nunez to left field, which the Giants hope will work and take away the need to trade for a left fielder. Why? Because their left fielders (mostly Chris Marrero and now-injured Jarrett Parker) were producing a .389 OPS through Sunday. Their center fielders (Span and Gorkys Hernandez) were at .478. The injury to Madison Bumgarner makes their getting to the postseason more difficult this season, but they’re built to win now and into the immediate future -- they can’t let it ride in the outfield.

The Nationals tried to land one of the big free-agent closers this winter, but when that fell through they looked from within to find an answer. They gave Blake Treinen an initial shot at being their closer, and he failed. Now manager Dusty Baker is giving opportunities to Shawn Kelley and Koda Glover. Although Glover could end up being an impact closer in time, the Washington front office knows this is a World Series-caliber team and has to be making phone calls to get a more proven closer. The Nats’ window to win could be just this year and next with Bryce Harper a free agent after the 2018 season. So it would be foolish for them not to take advantage of this window and make a trade. Unfortunately, to make one, they’re going to have to grossly overpay in prospects, just as they did in the Adam Eaton deal. But as I said then, if it means winning a World Series, who cares? GMs get paid to win world championships, not trades.

The Kansas City Royals are sitting in last place this morning, and although they do have a good enough club to be wild-card contenders, there’s no doubt the Indians are going to win the AL Central. Meanwhile, the Royals play every day knowing that Eric Hosmer, Mike Moustakas, Alcides Escobar, Lorenzo Cain and Jason Vargas (a top Comeback Player of the Year candidate) will all be free agents at season’s end. The Royals really can’t wait until the trade deadline to start making moves because they could wind up in serious competition with teams such as the White Sox and the Brewers, who are loaded with trade pieces. GM Dayton Moore said he was going to wait 30-45 days and re-evaluate the team at that point, but the inevitable is in front of him, as much as he might not like it. Two trips to the World Series and a world championship was a great tribute to Moore’s hard work in Kansas City. However, to get back there it’s time to make major trades for the future, as difficult and sad as that might be for Royals fans.

The Chicago White Sox have been holding out for what they believe is “fair” trade value for their roster filled with movable players, which means they risk being slow to pull the trigger unless they change their mindset. Getting maximum returns in the Chris Sale and Adam Eaton trades spoiled them, and they now expect that return in all their deals -- and that’s just not happening. Seeing Jose Quintana, Todd Frazier and Jose Abreu all get off to slow starts certainly didn’t help, which meant their phone has been quieter than expected to start the season. But there’s no doubt that the White Sox will make several deals between now and July 31, and they won’t be afraid to pull the trigger at any time if someone meets their asking prices.

The Seattle Mariners are the most intriguing team that could help itself with an early trade or two, because they too are off to a slow start. A lot of things have gone right for them, such as the emergence of right fielder Mitch Haniger and the great start by a healthy James Paxton. However, if they don’t start winning soon, Jerry Dipoto likes to deal more than any other GM in baseball, and he has significant players he could shop -- such as Nelson Cruz and Jean Segura. I think the Mariners will turn it around and get back in the race -- at which point Dipoto might instead look for trades to help his team win now.

Getting a deal done isn’t easy at this time of year because you need two GMs agreeing they’re better off dealing now as opposed to in July. But situations such as those of the Giants (a team that wants to win now and knows what it needs) or the White Sox (in which GM Rick Hahn knows he wants to deal veterans for a rebuild) suggest that some executives won’t wait until the summer to do something to help them execute their plan for the season.

Here is a quick look at the three teams most likely to be sellers between now and the trade deadline, and which players they might be trying to move:

Kansas City Royals

• Eric Hosmer, 1B: The problem is that no contending team is looking for a first baseman -- yet.

• Alcides Escobar, SS: The trade market is loaded with shortstops, including the Cincinnati’s Zack Cozart & Arizona’s Nick Ahmed.

• Michael Moustakas, 3B: If Pablo Sandoval doesn’t hit, the Red Sox could be a match; the Mets and Cardinals also could use him.

• Lorenzo Cain, CF: The Giants need him badly and could then move Span to left.

• Jason Vargas, LHP: One of the best stories of the year, and everyone needs a solid lefty starter.

Chicago White Sox

• Jose Quintana, LHP: A slow start doesn’t help his trade value, but the White Sox will still do well here.

• Derek Holland, LHP: He’s off to a great start, and if he keeps it up he should have real trade value.

• Dave Robertson, Closer: He is exactly what the Nationals need and has not given up a run.

• Jose Abreu, 1B: The slow start to his season suggests that if he does get traded it would be closer to the deadline.

• Todd Frazier, 3B: Another slow starter, but he’s a Jersey boy who would love to be a Met.

• Melky Cabrera, LF: The Giants don’t want him back, but he’d certainly help them.

Toronto Blue Jays

• Marco Estrada, RHP: No AL pitcher has a lower batting average against over the past two years. He could have great trade value.

• Francisco Liriano, LHP: He’s back, and his trade value will never be higher than right now.

• Josh Donaldson, 3B: The Blue Jays control him through next year, so I doubt they'd trade him unless overwhelmed by an offer.

• Troy Tulowitzki, SS: He’s in his decline years with a big contract; he won’t draw much interest.

• Jose Bautista, RF: He drew little as a free agent and is off to slow start.

Here are some players the Nationals and Giants could be targeting to fill their serious needs at closer and left field, respectively:

Washington Nationals’ possible closer trade targets:

• Tony Watson, Pittsburgh Pirates: He is a free agent at end of season and has gone 6-for-6 in his save opportunities with a 1.13 ERA.

• Alex Colome, Tampa Bay Rays: An obvious target, but the Nationals aren’t giving up top prospect Victor Robles to get him.

• Dave Robertson, White Sox: After overpaying for Eaton, they don’t want to do it again.

• Brandon Kintzler, Minnesota Twins: He’s a sleeper here but has not given up a run while going 4-for-4 in his save opportunities.

• The Oakland Athletics’ trio: Ryan Madson is signed through 2018 and off to a good start (1.23 ERA); Sean Doolittle looks as if he’s almost all the way back with 10 K’s in six innings; and Santiago Casilla, though inconsistent, is worth a shot if the price is low.

• Raicel Iglesias, Reds: He might be the only reliever they'd consider dealing Robles for.

• Trevor Rosenthal, Cardinals: He’s back to throwing 100 mph with command, but I doubt the Cards would move him.

San Francisco Giants’ possible outfield trade targets:

• Lorenzo Cain, CF, Royals: He would be a perfect fit, on and off the field.

• Melky Cabrera, LF, White Sox: They don’t want him back -- but they should.

• Jarrod Dyson, OF, Mariners: If Dipoto decides to sell, Dyson’s speed would fit well in the Giants’ outfield.

• Ryan Braun, LF, Brewers: They probably don’t have enough to get him, in money or in prospects.

• Andrew McCutchen, CF, Pirates: Though I’m not sure how the Pirates could trade him after Starling Marte’s suspension.

• Carlos Gomez, OF, Rangers: He’s off to a slow start in Texas but would be another good fit.

• Jose Bautista, OF, Blue Jays: His horrendous start wouldn’t scare the Giants away, not with his power.