His mechanics were off. He went in focused on finishing his release over his front side, but too often he was following through out wide. It was a bad session, but there were no opposing hitters to make him pay for his mistakes. He even said a bad side session rarely has any correlation with the upcoming game, but he was still angry.
"I love that," Collins said. "I love that about these guys. They demand perfection."
"Any pitcher who doesn't throw a good side going into a game doesn't feel happy about it," Wheeler said.
But he's still learning; still a "work in progress," as Collins said.
Part of the problem could lie in Wheeler overthinking the way he faces hitters. Too often, Collins said, pitchers focus on the hitters' weaknesses and not their own strengths. For a power pitcher like Wheeler, that means throwing more fastballs.
In his debut, 68.6 percent of his pitches were fastballs. Against the Nationals on Sunday, Wheeler only threw 66.3 percent fastballs -- the fewest of his young career.
"You have to pitch to your strengths," Collins said. "You can't always pitch to the hitters' weaknesses."
Even if Wheeler's and Harvey's personalities are distinctly different, Collins sees the similarities. Collins sees the "mean streak" Wheeler needs to succeed -- he plunked one of his own teammates during Spring Training -- and of course both dealt with or are dealing with unwieldy expectations.
"The expectations for this kid are out of sight, and in a year or so, they should be," Collins said of Wheeler. "Because he's got that kind of ability to make things special."
When Collins watches Harvey pitch, it's a reminder of just what Wheeler can become. Collins watched Harvey take his bumps and bruises in 2012 before blossoming into a National League Cy Young contender this year. They handle things differently, but Harvey and Wheeler have the same goals, and really, the same mentality. Harvey's separated himself now, but last year he was in the same place, and it didn't take him long to get past his worst days.
"We saw with Matt last year," Collins said. "Now look what we got."