It was hardly a secret that the Yankees needed starting pitching this winter. Their depth chart had a question mark at every rotation spot, and many members of the media, myself included, have assumed they'll pursue the top free-agent starter, Patrick Corbin. They struck early on the trade market by acquiring one of the best starters on that particular hot stove burner, James Paxton, but gave up their top pitching prospect to do so, along with another prospect with some real major league value.
The Yankees get two years of Paxton, and they seem to be acquiring him as he's reaching his peak: He has been worth 8.4 WAR, per Fangraphs, over 296 innings the past two seasons. It isn't unrealistic to think the Yankees can add five wins if they can get Paxton to make 30 starts next year. His fastball has averaged 94-96 mph the past three seasons, roughly the time when he has been an above-average or better starter, and he misses bats with it, pairing it with a cutter (kind of like a hard slider) and a big curveball that was supposed to be his out pitch when he was a prospect but hasn't been in the majors. He has also talked about using his changeup more in 2019, which would be interesting, though I'm not sure it is necessary for him to add a pitch. The Yankees needed rotation help, and they've clearly gotten some with Monday's trade.
Paxton's main issue is that he is frequently injured. He set career highs last year in starts, with 28, and innings pitched, with 160 1/3, which means he has never qualified for the ERA title. (Those are his major league highs; his highest workload in any pro season was in 2016, with 31 total starts and 171 2/3 innings between Triple-A and the majors.) He has had DL stints for a forearm bruise from a comebacker and a sore back in 2018; a forearm strain and a pectoral muscle strain in 2017; a strained middle finger tendon in 2015; and a lat strain that cost him more than half the season in 2014. If the Yankees expect 150 innings from Paxton and plan accordingly, this could be a perfect acquisition -- they do have a deep bullpen -- but they should assume that anything more would be a bonus.
The Mariners did all right here, getting two pitching prospects of merit back in the deal, both of them ready for some sort of major league role in 2019. I'm a Justus Sheffield fan and am definitely higher on him than the industry as a whole. But no matter what you think of him, he is clearly the Mariners' best prospect now -- probably their only top-100 prospect as of today. I've seen Sheffield up to 97 with a plus slider and above-average changeup, generally around the plate but with below-average command. He's a superb athlete and by all accounts a smart, coachable kid, the type of player who, in my opinion, is likely to make substantial improvements. If he gets to even average command, he's a mid-rotation starter trending to more. The lack of present command led two scouts to call him a "five-and-dive" guy -- meaning he's good for five innings and that's it. But we tend to ask starters to go only six in most cases anyway. He has the three pitches to start, a good delivery and enough control for it. So while any pitcher can end up in the bullpen, I don't see a good reason to forecast Sheffield there.
Erik Swanson works mostly at 90-94 but with good angle and spin to the pitch so that it plays up as plus or better, missing a lot more bats than the velocity might lead you to believe. He throws a ton of strikes and will show an average slider and changeup. His primary issue is that he's a fly ball pitcher who became homer-prone in Triple-A. That's less of a concern when his home starts will be in Seattle, a tough home run park, rather than Yankee Stadium, a good one. He's a back-end starter who might be more valuable in a relief role in which he can go multiple innings and potentially strike out 30 percent of batters or more, thanks to that fastball. Swanson lacks Sheffield's upside, but I think he's going to have a long career and might be a more predictable asset. Outfielder Dom Thompson-Williams is an org player with a little power who performed as a 23-year-old in A-ball.