Hellickson goes on DL, Grace and Collins return to bullpen

Jeremy Hellickson's hamstring strain was deemed to be "mild" by those looking at his MRI, but the veteran right-hander will need to miss at least a couple of starts and thus was placed on the 10-day disabled list today by the Nationals.

The Nats also sent right-hander Jefry Rodriguez (who impressively threw 4 2/3 scoreless innings in emergency relief of Hellickson on Sunday) back to Double-A Harrisburg and put relievers Tim Collins and Matt Grace back on the active roster for tonight's series opener against the Rays.

Hellickson's injury occurred four pitches into his Sunday start in Atlanta, when he pulled up lame after trying to make a lunging catch of Mark Reynolds' high throw to first base. Manager Davey Martinez and director of athletic training Paul Lessard wouldn't even let Hellickson try to throw a warmup pitch off the mound to test his right hamstring, instead signaling for Rodriguez out of the bullpen to make his major league debut.

After the game, Hellickson said he felt like this injury was far less severe than one he suffered in spring training 2011 with the Rays. He still was able to make 29 starts that season and win American League Rookie of the Year honors.

The Nationals don't expect the 31-year-old - owner of a 2.28 ERA in nine starts - to miss significant time, but they know he'll miss at least the next 10 days.

"It's a mild hamstring strain, so we'll treat it like that," Martinez said. "We don't know how long he'll be out. He's going to miss a couple starts. He's on the 10-day DL. We'll play it by ear."

Martinez also wouldn't commit to a rotation plan while Hellickson is out. Because of four off-days the next two weeks, the Nationals could go without a fifth starter until June 19 against the Orioles. Under that scenario, Max Scherzer, Stephen Strasburg, Gio Gonzalez and Tanner Roark would still each get to make at least one start on extra rest.

"We'll see where we're at," Martinez said. "I don't want to strain the workload on the guys we've got. These guys are doing really well. When we feel like we need to pop somebody in there, we will."

If they choose to go with another fifth starter, the likeliest choice would be Erick Fedde, who impressed in his sole major league start this season but did give up five runs on 10 hits in his most recent start for Triple-A Syracuse.

"As of right now, our bullpen's full," Martinez said. "We've got nine guys in our bullpen. And we'll determine who our fifth starter is going to be when we need one."

That bullpen now includes two left-handers who weren't part of the group Sunday: Collins and Grace. Collins returns after missing one game after his wife gave birth to a baby. Grace returns after a six-week stint on the disabled list with a groin strain.

The Nationals now have four lefties in their bullpen, with Collins and Grace joining Sammy Solís and closer Sean Doolittle.