On one hand, J.A. Happ is a 36-year-old pitcher whose fastball clocks in at about 92 mph.
On the other, opposing hitters can't seem to do much against that fastball -- even as Happ continues to throw it more and more.
Patrick Corbin's reported agreement with the Nationals pushes Happ toward the top of the free-agent starter market, and the lefty might be as good right now as he's ever been. Though he'll likely get a shorter-term deal with a higher average annual value, the adjustments Happ has made in recent years could help him age gracefully and prove to be a sound investment for his next club.
Teams will pay Happ based on what he can give them moving forward, but it's worth quickly examining what he's just accomplished. Among the 32 starters who compiled at least 500 innings over the last three seasons, Happ's 3.44 ERA ranks 10th, between Jonathan Lester and Jacob Arrieta. Looking one step further, Happ's .297 expected weighted on-base average -- or xwOBA, Statcast™'s all-purpose metric that considers walks, strikeouts and quality of contact allowed -- over the last two seasons puts him on par with Jameson Taillon, Zack Greinke and Gerrit Cole. Happ might not be a top-10 starter in the big leagues, but he can pitch like that at times and he certainly slots into the next tier. That's still a valuable free-agent starter that teams should go and get.

Happ wasn't always this good, but his late-career renaissance is based largely on how consistently he can attack hitters with his fastballs. Only four full-time starters threw more heaters than Happ in 2018, but the predictability didn't hurt his results: Opponents hit just .203 against that 92-mph four-seamer, which tied National League Cy Young Award winner Jacob deGrom for the eighth-lowest average allowed among more than 70 pitchers who navigated 200 at-bats with that pitch.
Happ also did something else that one rarely sees from a pitcher in his age-35 season: He set career-high rates in both whiffs per swing and overall strikeouts. The southpaw accomplished this by not only leaning on his four-seamer, but utilizing it in the most effective way for today's baseball environment. Check out how Happ has raised that riding fastball's location with each passing year: 
Gif: JA Happ Fastball Locations 2015-18
The above-average spin on Happ's fastball, paired with that elevated location, has been a load for hitters to handle. Opponents whiffed on 24.4 percent of their overall swings against Happ's four-seamer last season, but that figure jumped up to 36.2 percent when he was able to place it in the top-third of the strike zone and above. Happ's improved mechanics have helped him place his heater upstairs when he wants to, and that helped him place within MLB's top 10 in both swings and misses and popups induced by four-seamers this past season. Happ pairs that dominant upstairs heater with a sinker that gets as much vertical separation as anyone in baseball, and hitters have been on their heels even when they know some kind of fastball is likely on its way. This quote from Happ's former catcher, Russell Martin, to the New York Times sums it up well:
"If you're on the two-seamer, you'll get beat by the four-seamer. If you're on the four-seamer, then you're probably going to hit a ground ball with the two-seamer. And he just has a natural ability to elevate and throw it right in that spot where guys swing the bat. He hits the top of the zone -- sometimes he goes just above the top of the zone -- and he has enough life on it to just get it by guys."
There are a couple warning signs with Happ: His fly-ball rate inched upward in 2018, as did the percentage of barrels he allowed. But his increased strikeouts helped counteract those air balls, which are in some part a natural byproduct of pitching more at the top of the zone. By and large, Happ's pitching style appears ideally suited for this launch-angle era for hitters, and his velocity has remained consistent over the past five seasons (it's actually better than it was in his 20s). Even if that velocity dips a little moving forward, Happ's spin and location could help him continue to miss bats.

Industry evaluations project that Happ will receive a two-year contract worth somewhere around $28-30 million this offseason, and if he pitches anywhere close to the 3-WAR pitcher he's been over the past two seasons, he could easily exceed that value. Fangraphs' Steamer system projects Happ to be slightly more valuable than he was in 2018, with somewhat similar strikeout and walk rates. 

With Corbin now off the table, the Yankees seem like the ideal landing spot. Happ might not be a No. 1 starter, but he wouldn't need to be in a New York rotation already stocked with Luis Severino, James Paxton and Masahiro Tanaka. And it's hard to discount what the Yankees just saw from Happ as he posted a 2.69 ERA over 11 starts for them down the stretch after they acquired him from Toronto. Perhaps Happ's addition would help to diversify the Yankees' rotation and keep its pitch mixes from becoming too predictable to AL East opponents.
The Yankees aren't the only team who could use Happ, of course. The Phillies are rumored to be just as interested, while the Blue Jays would surely welcome him back and the Astros have a couple holes to fill in their rotation, too. Happ appears to be the rare 36-year-old whose stock is peaking, and he could prove to be the affordable starter who makes his next team look smart by this time next year.