This is the second time Simontacchi has had an ailment this season. In late June, Simontacchi had to get extra rest because his right shoulder was fatigued. With this latest ailment, Simontacchi is expected to miss one turn.
Simontacchi said he started feeling pain in his elbow against the Brewers on July 7 and felt it again last Sunday against the Marlins.
"I figured it was just a little swelling and inflammation and that's all it was, and I just kept going," Simontacchi said. "It's just a matter of getting the inflammation out and letting nature take its course."
For the season, Simontacchi is 6-7 with a 6.37 ERA. In his last start, Simontacchi lasted 4 1/3 innings and gave up five runs on nine hits against the Marlins on Sunday afternoon.
As for Traber, he will be making his first start since late last season. He had serious problems in that role, going 3-3 with a 7.75 ERA, but he has been a valuable reliever since then-manager Frank Robinson put him in the bullpen in September. This year, Traber is 2-0 with a 4.70 ERA. He usually pitches in long relief and faces only lefties in certain situations.
On the mound: Ross Detwiler, the team's first-round pick in the 2007 First-Year Player Draft, made his Major League debut Thursday for the Gulf Coast Nationals. The left-hander pitched two shutout innings and struck out three batters.
Welcome back: The Nationals signed right-hander Hector Carrasco to a Minor League contract on Wednesday. Carrasco returns to the Nationals after spending more than a year with the Angels, who designated him for assignment more than 10 days ago.
Carrasco had his best season in a Nationals uniform. In 2005, the 38-year-old went 5-4 with a 2.04 ERA in 64 games as a reliever and starter. Carrasco often credited pitching coach Randy St. Claire for teaching him a changeup, which led to the great season.
Stat of the day: The Nationals are 16-12 in one-run games.
Did you know? Austin Kearns leads the Nationals in outfield assists with seven.
Coming up: The Nationals play the second game of a four-game series against the Rockies at 7:05 ET on Friday night at Robert F. Kennedy Stadium. Traber will face Colorado right-hander Aaron Cook.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.