After it looked as though the Cardinals had other options in Shelby Miller and Joe Kelly, manager Mike Matheny made the decision to move Rosenthal to the bullpen and utilize his ability to throw 100 mph fastballs in late-inning situations.
Rosenthal did exactly that on Tuesday night in his season debut, pumping in two pitches at 100 mph while dominating helpless Arizona Diamondback hitters.
Rosenthal tossed a perfect eighth inning, throwing just nine of his 13 pitches for strikes and struck out two Arizona hitters.
Rosenthal now will be the eighth inning man as the Cardinals' regular set-up man Mitchell Boggs fills the closer's role in Jason Motte's absence.
Rosenthal certainly looks more than capable of handling the job and it should be fun to watch just how often he rings the 100 mph register in 2013.