The Chicago White Sox signed Welington Castillo, my No. 25 free agent, to a two-year deal with a club option, valued at $15 million right now with the option buyout included. It's the best deal of the offseason to date. Granted, it's the only deal of the offseason to date, but we need to celebrate what we have, not what we don't, and I do still really like this deal for the Sox.

Chicago had no viable starting catcher on their roster to end 2017, with two backups, Kevan Smith and Omar Narvaez, the only catchers on its 40-man before this signing. Castillo hits like a regular, and has a plus arm, but he's a poor framer and has no real history of playing every day in pro ball. If you think you can stretch him to 120 games without losing any productivity, he's easily a $10 million player, even for a team like the White Sox that isn't contending in 2018. (As the saying goes, every team needs a catcher, or else they'll have a lot of passed balls.)

Castillo will be replacing replacement-level players, and it won't be hard for him to justify a $7.5 million average annual value (AAV), even with below-average pitch framing. We've seen over the course of the past few years that catchers can improve their framing skills, even at an age when most skills have stopped improving, and that good framing can disappear overnight, which means paying face value for it may not be as smart as it appeared two years ago.

The deal also allows the White Sox to shop Castillo multiple times rather than just at this year's trade deadline, which would have been the case on a one-year deal. With only one catching prospect of any note in the system -- Zack Collins, himself a poor defensive catcher -- there's no impetus for them to move him immediately unless they're blown away by an offer. They can utilize Castillo until they have an adequate replacement and then try to flip him for a prospect.

When the St. Louis Cardinals signed Dexter Fowler last December, I wrote that Aledmys Diaz was probably going to regress from his 2016 performance, and he did, losing his starting job at shortstop, then his roster spot, and now his entire place in the St. Louis organization, as the Cards traded him to the Blue Jays for a non-prospect right before the tender deadline.

Diaz isn't arbitration-eligible yet, but his just-expired contract paid him $2 million in 2017, so he will make something close to or just below that in 2018. He wasn't worth that to the Cardinals, who have Paul DeJong locked in at short and are already paying Kolten Wong more than they'd like at second base. The Blue Jays, on the other hand, have a regular shortstop who played just 66 games last year and wasn't very good when he did play. Troy Tulowitzki has become more known for his injuries than his production; in three of the past six years, he's failed to appear in at least 100 games.

Diaz is a high-contact hitter with a little pop and poor patience, and he can play fringy defense at short, all of which makes him a very good understudy to Tulowitzki, capable of filling in for Tulo during short or long absences. He fits the Jays' roster much better than he fits the Cards'.

St. Louis gets back outfielder J.B. Woodman, the Blue Jays' second-round pick from 2016 (unranked on my top 100 before the draft). Woodman played in low-A last year at age 22 and hit .240/.320/.378 with 157 strikeouts in 411 plate appearance while posting a 38 percent strikeout rate that was third-highest in the Midwest League. He can show four tools -- run, power, field, throw -- but he was old for the level and didn't make as much contact as players three or four years his junior. I don't see him as a future major leaguer.

Lastly, the Tampa Bay Rays and Arizona Diamondbacks pulled off a trade. Reliever Brad Boxberger had a dominant season in 2014, striking out 42 percent of the batters he faced, then he became the Rays' closer in 2015, where he was less effective across the board. In the past two seasons, he's thrown just 53 ⅔ major league innings in total, with 62 strikeouts, 26 unintentional walks and seven homers allowed, missing half of 2017 with lat and forearm injuries and more time in 2016 with an oblique injury.

Boxberger is a reverse-split pitcher, meaning that even though he's right-handed, he's been much more effective against left-handed hitters in his career. If he can stay healthy enough to throw 50 innings, Boxberger should give the Diamondbacks some league-average middle relief work. He has two years of arbitration eligibility remaining before he becomes a free agent after the 2019 season.

In exchange, the Rays got right-hander Curtis Taylor, my No. 10 D-backs prospect last winter. He's a sinker/slider guy who will touch 96 mph with his fastball when working in relief. He made 13 outings as a starter in the middle of 2017 before he was shut down for the rest of the year with a shoulder impingement. If poor arm health pushes him back to the bullpen, he could move up to the majors at some point in 2018. For the Rays, keeping and paying Boxberger made zero sense; getting an actual prospect in return for him is a bonus.