WEST PALM BEACH, Fla. -- This was his first time on the mound in a big league game since August 2017 and Trevor Rosenthal wanted to ease back into things. Yet when he peaked at the scoreboard here at the FITTEAM Ballpark of the Palm Beaches, after missing out of the zone on back-to-back pitches against Evan Mendoza, the right-hander saw triple digits flash across the screen.

“I was kind of surprised at how hard I was throwing,” he said. “I didn’t really want that, either. I just wanted to kind of ease into it. But I guess it happens.”

The ability to hit 99 or 100 mph “happens” for so few pitchers that the Nationals were more than happy to pounce at the opportunity to sign Rosenthal even though he missed all of 2018 after undergoing Tommy John surgery. It’s the same elite velocity he flashed during a showcase for teams in Southern California in October, which convinced the Nats he was healthy. They quickly signed him to pair with Sean Doolittle at the back end of their bullpen, and they have been happy with their investment so far this spring.

Rosenthal tossed a 1-2-3 fifth inning in his debut Tuesday afternoon against the Cardinals, reaching that 100 mph plateau with ease en route to a strikeout and a pair of groundouts. More importantly, Rosenthal is showing no lingering effects this far removed from the injury and looks poised to regain the form that made him one of the elite relievers in the game.

"What's good about that whole deal is that he thought he was throwing 94-95 mph," manager Dave Martinez said. 

“I feel really strong right now, honestly," Rosenthal said. "I feel like if the season started tomorrow, I’d be fine. That might just be the competitor in me. But I’m going to trust [pitching coach Derek Lilliquist]. He’s luckily seen me my whole career, so I think he’ll put me in a good spot to handle Opening Day and finish the season strong.”

Rosenthal might feel ready to get the regular season going, but he's also focused on not overdoing things and continuing to work on the plan and schedule the Nats have developed to keep him healthy heading into the season. When Rosenthal stepped on the mound Tuesday afternoon, he did not consider how long it had been since he had reached that level -- 18 months since he had last been on a big league mound -- or that he was facing his former team in the Cardinals.

“I’m really excited about this team and how good we have the potential to be,” Rosenthal said. “Just trying to be a part of that and fit in and do my part. That’s really what has me excited. The injury, I mean, it’s definitely cool to be back. I’m excited to get that out of the way. But I’ve been throwing so much that it kind of feels like just another day, unfortunately.”

Martinez got to see the potential of his new bullpen “big three” of Doolittle, Rosenthal and Kyle Barraclough, the three relievers he expects to lean on most heavily to navigate through high-leverage situations. All three appeared in Tuesday’s game, and each tossed a scoreless inning with a strikeout -- Doolittle in the third, Rosenthal the fourth and Barraclough in the fifth.

But the potential of this bullpen rests on Rosenthal. If he can return to his pre-Tommy John form, the Nationals could have one of the strongest late-inning tandems in the National League. They might not have the depth in the bullpen to be effective bridging the gap to Doolittle if Rosenthal falters.

"He's going to be really important. He really is," Martinez said. "I just want him to continue -- obviously he came out today and hit that triple digit. It's early. He feels good and I want him to continue to feel good going into the season."