WASHINGTON -- A wobbly Cardinals bullpen got a boost on Monday with the return of right-hander Trevor Rosenthal, who was activated from the 10-day disabled list before the club opened a three-game series against the Nationals.
The Cardinals optioned Sam Tuivailala to Triple-A Memphis to make room for Rosenthal on the 25-man roster.
Rosenthal got involved right away, summoned to throw the seventh in an eventual 14-6 loss to the Nationals. And on a night when the Cardinals' bullpen allowed eight runs, Rosenthal was the bright spot.
He struck out the side on 14 pitches and lit up the radar gun immediately. Rosenthal averaged 98.4 mph on the dozen fastballs he threw and hit as high as 99.9 mph, according to Statcast™. He garnered four swing-and-misses on the pitch.
"I felt pretty good," Rosenthal said afterward. "I'll continue to hopefully get in a rhythm and build off of that. I definitely want to fine-tune some things. But I think it was a good first step. It's good to be back out there."
Plans for Rosenthal to rejoin the team on Monday were set into motion after he looked strong while facing teammates during a simulated inning on Saturday. That followed the pair of bullpen sessions he threw earlier in the week. Rosenthal increased the intensity with each subsequent session.
The Cards placed Rosenthal on the 10-day disabled list on March 30 due to recurring tightness around his right lat muscle. He had Spring Training interrupted by the same injury, but he said the second occurrence was not as severe as the first.
Nevertheless, it has altered his role.
The Cardinals began Spring Training wanting to see how Rosenthal would fare over longer appearances. He was briefly considered a candidate for the team's open rotation spot and as a potential flex reliever who could pitch multiple innings as a bridge to the back end of the bullpen.
But with concerns about how his body responded to that push during spring, the Cardinals are now backing off those plans.
"With the physical hang-ups that we've had here with Trevor, it doesn't make a lot of sense early on that that's how he's used," manager Mike Matheny said. "That was kind of the plan going in, trying to stretch him a little bit. Now, it's about health. And for his health sake, we're going to have to be careful with how much we're using him early on."

One way Rosenthal could improve his flexibility and availability is through increased efficiency. He averaged 21.3 pitches per inning last season, a jump from the 17.5 pitches-per-inning average he posted in 2015. Harnessing the pitch count as he did in Monday's appearance could create opportunities for Rosenthal to get multiple-inning opportunities later in the season.
"He can be as good as anybody in the game in just about any role, as far as the bullpen is concerned," Matheny said. "'I'm just anxious to get him in there. We'll have to watch his workload at the beginning. Right now, we're happy that he's healthy and an option."