What in the world has happened to Twins pitcher Kyle Gibson?

Kyle Gibson went 13-12 with a 4.47 ERA as a 26-year-old pitcher for the Twins in 2014, then followed that up with an 11-11, 3.84 ERA season at age 27 in 2015. He struck out batters at a higher rate (6.7 compared to 5.4) in 2015 and appeared to be on his way toward settling in as a middle-of-the-rotation pitcher for years to come.

In 31 starts since — including an ugly four inning, four run effort Thursday — Gibson has regressed (and that might not be a strong enough word for it). If he was pitching to keep his spot in the rotation after a particularly ugly beginning of the 2017 season, the result says he no longer belongs.

So what happened? That's the hard part.

FanGraphs data shows his fastball velocity has been fine this year, right in the 91-92 mph range it was when he was having more success. He's throwing a few more sliders and curveballs while offering up fewer change-ups this season than in past years, but he's still throwing 56 percent fastballs. In 2015, that number was 58 percent. So maybe he's changed his approach some, but not much.

The Twins have harped on him to get ahead in the count and to throw quality strikes. Before Thursday's game, manager Paul Molitor talked about fastball command as an issue for Gibson.

He tried a new training regimen this offseason and had a strong spring — giving up just five runs in 28.1 innings. But once the regular season started, the 2016 struggles resumed and then got even worse.

It's puzzling. Maybe the Twins overvalued him a little, but it seemed like the worst-case scenario was that he would become more of a back-end rotation pitcher. Instead, a pitcher who figured to be ascending through these years — he turns 30 in October — has gone from rotation mainstay to giant question mark.