But when the right-hander is able to stay focused, deliver his pitches exactly where he wants them and excel in the mental aspect of the game, he can have outings like he had in Friday's 4-2 win over the Padres.
De La Rosa pitched seven innings, allowing two runs, one earned, on five hits with six strikeouts, and earned back-to-back wins for the first time since his first two starts of the season. He has given up just one earned run over his last 15 innings.
"He's getting better mentally because he's always had really good stuff," D-backs catcher Welington Castillo said. "That's part of my job to calm him down because it's not easy to get rid of bad habits. I just try to calm him down and let him make the pitch that he needs to make."
The pairing of De La Rosa and Castillo, who have known each other since their Little League days in the Dominican Republic, seems to be working well.
"For me, it's good to have a guy like [Castillo] try to make me comfortable on the mound, try to use all my pitches and make them when it counts," De La Rosa said. "It makes me more confident than before."
In his last start, De La Rosa threw eight scoreless innings against the Giants. But there has still been some inconsistency for the 26-year-old. In the two outings before that, he allowed a total of 16 runs in 10 innings.
But it's the first time in his five-year career that De La Rosa is a fixture in a team's starting rotation.
"He's just a young guy finding his way," D-backs manager Chip Hale said. "We've committed to him and he's having some rough spots, of course."
There's no question, however, that De La Rosa has good stuff. His fastball was hitting 99 mph and his slider has shown improvement.
Sometimes though, little mistakes have escalated into much worse incidents. There was potential for that in the fifth inning when De La Rosa gave up a two-out single to Padres starter James Shields, then three batters later walked in a run that cut the D-backs' lead to 4-1.
But De La Rosa struck out Matt Kemp to leave the bases loaded and didn't allow a hit the rest of the night.
"He got out of it, that's a big step forward. I think Welington really helped him there to just allow the one run," Hale said. "He had good stuff until the end."