Right-hander Jordan Zimmermann complained about having a dead arm earlier this spring. His arm was back to life by mid-March, however, and the Nationals are optimistic that's a sign that he's headed toward another strong season.

Zimmermann turned in a spectacular six-inning effort against the Detroit Tigers on March 18. He gave up a single to the first batter, then retired 18 in a row with little trouble.

His arm appeared to be doing better, and Zimmermann looked more like he did last year, when he went 12-8 with a 2.94 ERA in 32 starts.

"I had all four pitches working," Zimmermann told reporters. "It's one of those days when you have everything working. You can locate everything anytime you want. It's hard to come by ... They don't come often, let's just say that."

There's no question that the Nationals will have one of the best rotations in baseball. Stephen Strasburg and Gio Gonzalez are the top two starters, but Zimmermann is right there with them.

Zimmermann is coming off a solid 2012 season in which he posted the National League's seventh-best ERA. He would have won more games if the Nationals had given him better support on offense, a problem that kept cropping up all season.

Washington was fortunate last year in that the rotation had almost no injuries. Strasburg was coming back from his arm surgery late in 2011, and he pitched well in 2012 before the team shut him down in September in a controversial move.

Strasburg, Gonzalez and Zimmermann can all remain healthy through the entire 2013 season, the Nationals will be in good shape in their defense of the NL East title.