It's "best tools" week! For a second straight year, Keith Law lays out his rankings (and reasonings) for the players with the best tools in baseball. Earlier this week, he ranked players in the four key hitting/speed tools that scouts use to evaluate players. Today he looks at the fielding tools: top gloves and arms at catcher, the infield and the outfield. (See last year's fielding rankings here).

Best catcher glove

1. Buster Posey, Giants
2. Yadier Molina, Cardinals
3. Russell Martin, Blue Jays
4. Jonathan Lucroy, Rangers
5. Francisco Cervelli, Pirates

These five catchers are all above-average receivers, framers and game-callers, and all have been doing it for a little while (or a long while), giving me more confidence in the rankings here, because it is one of the hardest tools to evaluate visually and the statistics we have to measure catcher defense remain imprecise and/or nonexistent. As with last year's list, Yasmani Grandal, an excellent framer, doesn't make the cut, because he's a poor receiver and even worse at calling a game. Salvador Perez, praised as a good receiver, doesn't make the cut, because he's a consistently below-average framer. Kevin Plawecki might have made this list if Mets manager Terry Collins hadn't killed him in May with his comments to the media.

Best catcher arm

1. Yadier Molina, Cardinals
2. Salvador Perez, Royals
3. Matt Wieters, Orioles
4. Gary Sanchez, Yankees
5. Christian Bethancourt, Padres

Molina's good enough at controlling the running game that runners tend to attempt fewer steals against him. They haven't learned that lesson with Perez, who has nailed 31 of 61 baserunners this season. The next three guys on the list all have very strong arms but aren't as effective as the first two in actually nabbing would-be thieves. Bethancourt has the best arm strength of any catcher I've seen, but still takes longer than he should to get rid of the ball. If you could give him the release of Posey, who doesn't have huge arm strength but gets rid of the ball quickly, no one would ever run on him. Cubs rookie Willson Contreras could also be put on this list.

Best infield glove

1. Andrelton Simmons, SS, Angels
2. Manny Machado, 3B/SS, Orioles
3. Nolan Arenado, 3B, Rockies
4. Brandon Crawford, SS, Giants
5. Francisco Lindor, SS, Indians

We're in a golden era of infield defense right now. Look at some of the names who didn't make the list: Jose Iglesias, Dustin Pedroia, Adrian Beltre, Anthony Rendon, Zack Cozart, Adeiny Hechavarria, Addison Russell, Nick Ahmed. Plus fielders, all of them. (Perhaps plus is the new average.) Simmons remains the gold standard for defense, the best defensive infielder we've seen since Ozzie Smith, but Machado is his analogue at third base and could return to shortstop full time if the need arises.

Infield arm

1. Andrelton Simmons, SS, Angels
2. Manny Machado, 3B, Orioles
3. Nolan Arenado, 3B, Rockies
4. Anthony Rendon, 3B, Nationals
5. Troy Tulowitzki, SS, Blue Jays

I've talked enough about Simmons throwing 98 mph as an amateur pitcher/shortstop at Western Oklahoma. Machado and Tulowitzki had the strongest throwing arms I've seen on an amateur player in person -- I didn't see Simmons before he signed -- and Rendon's arm strength and overall defensive prowess have been lost a little beneath all his injuries.

Outfield glove

1. Kevin Kiermaier, Rays
2. Billy Hamilton, Reds
3. Jason Heyward, Cubs
4. Kevin Pillar, Blue Jays
5. Mookie Betts, Red Sox

The first four were easy. Kiermaier has become a historically great defensive outfielder, and Hamilton is the fastest player in the majors, perhaps in MLB history, and has the range that such speed confers on a fielder. As for the fifth spot, it could have gone to a number of players, but I went with Betts, in part, because he has shown he can handle center field as well as right and is such a good athlete that he could probably play any position the Red Sox ask him to play.

Outfield arm

1. Bryce Harper, Nationals
2. Leonys Martin, Mariners
3. Aaron Hicks, Yankees
4. Kevin Kiermaier, Rays
5. Adam Jones, Orioles

Harper, Hicks and Jones all pitched as amateurs, so it's no surprise to see them all turn into hard-throwing outfielders, with Harper and Jones bringing more accuracy and Hicks just bringing heat. Adam Eaton and Colby Rasmus would be in the next tier, as would Byron Buxton and Carlos Gomez if either were on a major league roster at the moment.