After discussions with bullpen coach Darren Holmes, De La Rosa dropped a hesitation in his delivery. In three relief appearances, he held opponents to one run and three hits -- with 10 strikeouts and no walks -- in eight innings. In his last outing, De La Rosa replaced struggling starter Chad Bettis and held the Pirates scoreless for four innings, with five strikeouts, in an 11-5 Rockies victory Thursday.
"I feel good right now," De La Rosa said after a throwing session on Sunday. "I just have to keep doing the same thing I was doing when I was pitching from the bullpen."
De La Rosa was 1-4 with an 11.41 ERA in six starts. Five came before a stint on the disabled list with a left groin strain, with the Rockies hoping De La Rosa could find his form in Minor League rehab games. But the time in the bullpen allowed De La Rosa to make necessary changes.
"All the things that we've asked him to do, we've seen those things," Rockies manager Walt Weiss said. "We've seen the tempo pick up. We've seen the use of the fastball, the use of the curveball. He's more efficient.
"He's done his part. He's got a great track record. We lean on that. We feel he's ready to go."
De La Rosa has overcome poor early season starts before en route to holding Rockies records for wins (80) and wins at Coors Field (50), but the severity of this start forced him to make the significant change to his windup.
A hesitation in a delivery can throw off a batter's timing, but De La Rosa's arm was having a hard time catching up to the rest of his body.
"It didn't take me that long to get used to it," said De La Rosa, who will make his 100th career appearance at Coors Field on Tuesday. "I've been working with Holmesie in the bullpen almost every day. He said a lot of good things to me, and that's helped me."
For the season, his average fastball speed is 90.4 mph, which is what De La Rosa threw during three late-season starts in 2012 after recovering from Tommy John surgery. But against the Pirates, he was clocked consistently at 91-92 mph, which set up a low-80s split-finger pitch and a curve in the 70s. Not only was there greater fastball velocity, but he hit his location more consistently.
"In the beginning, everything was bad," De La Rosa said. "My mechanics were bad. That's why the location wasn't there. My arm speed was bad. Right now, I feel better, stronger and like just a better pitcher."