PHOENIX -- Padres right-hander Jarred Cosart was placed on the 10-day disabled list Tuesday with a right elbow strain. The club selected the contract of outfielder Jose Pirela to fill the open roster spot, and it appears likely that rookie right-hander Miguel Diaz will make his first Major League start in Cosart's place Saturday.
The extent of Cosart's injury is unclear, but he will be shut down for at least a week before he is re-evaluated. Cosart struggled in his last three starts, walking 12 hitters over 10 2/3 frames. In seven outings this season, he has posted a 4.88 ERA.
Cosart had surgery on his right elbow to remove a bone spur during the offseason, one of a handful of injuries that have plagued his tenure with the Padres. He missed time earlier this season because of a right hamstring strain, and also suffered a groin injury last September.
"Cosart's just had some elbow issues he's dealt with, honestly, for the last couple years," manager Andy Green said. "He still has some things that are bothering him in there."
In Cosart's absence, Diaz, a Rule 5 pick, follows the path blazed by Luis Perdomo last year. Like Perdomo, the Padres view Diaz as a starter, but they initiated him into the Major Leagues with a bullpen spot, easing the jump from Class A to the Majors.

Diaz owns a 7.83 ERA in 20 appearances out of the bullpen this season. Like Perdomo a year ago, Diaz struggled early, but has settled in nicely in May. Perdomo was inserted into the rotation early last June when Andrew Cashner was placed on the disabled list. Now, it appears Diaz will get his shot.
"He's got a lot of things that provide intrigue to us, as a starter," Green said. "We're going to take a look at that at some point in time. There's a good chance it's this Saturday."
To clear room for Pirela on the 40-man roster, the Padres transferred outfielder Travis Jankowski to the 60-day DL. Jankowski has a fracture in his right foot, and he won't resume baseball activities until late June, at the earliest.
Pirela batted .331/.387/.635 in 48 games for Triple-A El Paso this season. He played in 15 games for the Padres last year, going 6-for-39. He was in the lineup, batting sixth, for Tuesday's night series opener against the D-backs at Chase Field.
"That's what everyone wants, to get here to the big leagues and to be playing right away," Pirela said. "You just show what you can do, take advantage of the opportunity and show that you have things to bring to the team."