Worley was coming off surgery to remove bone chips in his throwing elbow the previous September, and Mason thought Worley's arm slot was too high, which wasn't allowing him to get the ball down and was hurting his velocity.
Worley noticed a difference immediately thanks to Mason, as he saw his fastball jump from topping off in the low-90s to the mid-90s, and he fared better at Rochester with a 3.88 ERA and three complete games in nine outings.
"For as much as he doesn't want credit for it, he looked at films from previous years and that season, and he saw two outings in Triple-A and said, 'This is what I think I see. We'll see what it's like in the 'pen,' and everything worked out from there," Worley said. "But then the next thing you know, it was my shoulder."
As Worley noted, he didn't get a chance to keep working on pitching with his improved arm slot, as he was shut down for the season in early July with shoulder inflammation. He also believes his arm wasn't ready for the improved arm speed, which led to the injury.
"I went from throwing 88-90 mph to 95-96, and that's when I started to have some problems," said Worley, whose fastball averaged a career-low 89.5 mph with the Twins last season, according to Fangraphs.com. "I started to develop that arm velocity again, and I wasn't used to it and couldn't handle it."
But Worley spent all offseason working on keeping the ball down, and said he's been getting better velocity on his fastball this spring and he feels fully healthy for the first time since he joined the Twins in the trade that sent Ben Revere to the Phillies before the 2013 season. He also lost 25 pounds over the offseason in an effort to improve his conditioning.
"Last year, I was just trying to learn how to throw again," Worley said. "My arm slot was too high. Everything was up. This year, I'm bouncing it, which is something I didn't do last year. So I'll take that over something up in the zone."
This spring is an important one for Worley, who is out of Minor League options and is competing for the fifth spot in the rotation along with Samuel Deduno, Scott Diamond and Kyle Gibson.
Deduno and Diamond are also out of options, so the battle for the fifth spot in the rotation could mean that the two who don't make the rotation could be placed on waivers or moved to the bullpen.
"[We] have roster issues, guys that are out of options, but I think you take the best player," Twins manager Ron Gardenhire said. "Best pitcher. That's what we have to do. We've lost enough. Now it's time to take the best pitchers."
Worley was solid in his three years with the Phillies with a 3.50 ERA in 53 career outings, including 46 starts, but he failed to replicate that success in a Twins uniform last year.
He was off to a strong start this spring before getting knocked around by the Pirates in his latest outing on Friday, as Worley lasted just 1 1/3 innings and gave up five runs on seven hits and a walk.
Worley suffered from some bad luck with a pair of RBI singles that didn't leave in the infield in the first inning, but he also gave up a hard-hit double to Andrew McCutchen in the first and a two-run blast to McCutchen in the second.
"They blooped some balls in and had some choppers in the infield, and it's early in Spring Training, but we want to see better than that." Gardenhire said. "But he has a better angle and the ball is going down better. And that was evident by the choppers. But he still got some balls up that were hammered."
Worley said he was affected by the high winds at McKechnie Field, but he also knows that excuses won't cut it, as he has to prove he's worthy of the fifth spot in the rotation no matter the conditions this spring. He currently has a 10.38 ERA, but in just 4 1/3 innings, so there's still plenty of time to improve after his shaky start on Friday.
It figures to be a close battle for that fifth spot, and Worley is doing his best not to think about it.
"At this point, it's out of my control," Worley said. "It's going to be who the best is this spring, and that's who it's going to go to. I'm just worrying about getting outs and staying healthy."