Before that home run, though, came too many pitches, 23 in total to the first three batters Rosenthal faced. Ramon Flores struck out to open the inning, but saw 10 pitches in the process. A seven-pitch battle against Yadiel Rivera ended in a groundout. Rosenthal then lost Kirk Nieuwenhuis after getting ahead, 1-2, in the count.
Of the five batters Rosenthal faced, four went to three-ball counts. The lone exception was Santana, who clobbered a high fastball on an 0-1 count. Last year, Rosenthal allowed three home runs over 287 plate appearances.
"Most of the guys I faced, I threw too many balls and got behind in counts," Rosenthal said after the loss. "I kind of gave them an advantage there, I feel like, to get something going, see some more pitches."
Manager Mike Matheny pulled Rosenthal after he issued another walk on his 33rd pitch of the inning. It was his second 30-plus pitch appearance already this season. Last year, Rosenthal eclipsed that total once, that coming in his first outing after an extended All-Star break.
"It's a reminder of how hard this is," Matheny said. "He's going to have to continue to figure out ways to get ahead in the count. That's his game. And then once he does, [the opponents'] chances of success go way down for as many pitches as he has -- with the effectiveness of the changeup, the cutter and the curveball. But when you get into tough counts, it's hard to use those other pitches."
Rosenthal has worked into three-ball counts against six of the 19 hitters he has faced in his first four appearances. That percent (32) is significantly higher than it was last year, when 21 percent of batters extended the count to three balls against him.
"He's been so efficient, especially last year, and did such a good job working ahead," Matheny said. "Stuff looked good. It's just going to be getting it on the plate."
Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, follow her on Twitter @LangoschMLB, like her Facebook page Jenifer Langosch for Cardinals.com and listen to her podcast. This story was not subject to the approval of Major League Baseball or its clubs.