It did not take long to figure out why he had made the leap from Double-A. Rosenthal's fastball was registering from 97-99 mph, most often 98. And that was far from all that he had.
Rosenthal got his chance Wednesday in the final game of the series. He wasn't given a mop-up, low-leverage situation, either. Matheny demonstrated confidence in him by putting him into a game that was still a game; the Cardinals trailing, 4-2, the Brewers batting in the bottom of the eighth.
Rosenthal gave up a walk and a scratch single to open the inning, then struck out Corey Hart and got Rickie Weeks on a liner. But a walk to Martin Maldonado loaded the bases. At this point, Matheny went to the mound, and the thought automatically occurred that he would make a change. But that wasn't the deal at all.
"I just wanted to tell him to slow down a little bit," Matheny said, and then smiled slightly. "He probably doesn't remember a word I said. It was just to let him stop and breathe for a second."
In fact, Rosenthal had a decent grasp of what the managerial visit meant. "I appreciated that little breather," he said later. "It kind of slowed me down.
"He just told me I had that guy there [Carlos Gomez] and to take a breather. He said he knew that I could get him out and just to keep pitching."
The record will show that, during the ensuing at-bat, Gomez hit a breaking ball deep down the line in left that hooked enough to avoid being a grand slam homer. But the record will also show that Rosenthal came back with another breaking ball, a better breaking ball, that Gomez chased for strike three. End of inning. Beginning of what could be a very big career for Trevor Rosenthal.
"I thought he did a great job," Matheny said. "We put him in a tough spot there. It's a tough spot for any player the first time they get out there, a lot of different emotions. He wanted to prove himself to us and to do what he could to help us. He did well harnessing it, coming back and making some good pitches. He did a very nice job.
"He wasn't just dead-brain heaving. He was making pitches. He gave up a long foul to Gomez on a breaking ball, then struck him out with another one."
"It's an experience I'll never forget and I'm just really blessed to be in this situation," Rosenthal said. "It's an honor to share it with the guys on this team. It's one of those moments that I'll never forget."
But what made this even better was the confidence in Rosenthal that Matheny had displayed twice; once by putting him into a crucial situation, and then by staying with him when the bases were loaded. Rosenthal was suitably appreciative.
"That's huge," Rosenthal said, "that he has the kind of confidence to have me here in the first place, and then to keep me in that situation and have the confidence that I'll get that out."
The Cardinals didn't win this game, but there was still something achieved here.
"I'm a big fan of the guy that he is and the pitcher and the player," Matheny said. "I think he can be around this game for a while. It was nice to get him an opportunity. I did want to make a statement to him that he can pitch at this level. And he can get himself out of a spot like that. He did it and hopefully that sticks with him."
Rosenthal will occupy a place in history by virtue of this appearance. He became the 2,000th player to appear for the Cardinals franchise. According to BaseballReference.com, the Cardinals are the first Major League team to have 2,000 individual players.
That's a nifty historical niche. But for future reference, Rosenthal has a chance to be remembered for much more than that. And the beginning of his Major League career received a major boost from a manager who was willing to act on his confidence in a rookie, no matter how difficult the circumstances appeared.