With the Padres' relief corps in need of a respite, Diaz was activated before Tuesday's game, with shortstop Dusty Coleman optioned to El Paso. Diaz will likely be used out of the 'pen over the next couple of days, though it's still a possibility he returns to the rotation next month.
"Right now he's in the bullpen," Padres manager Andy Green said. "We've thought about bringing him back in the rotation, but we got to a point where we needed [relief help]."
Diaz, the top overall selection in the Rule 5 Draft, began the season as a reliever before transitioning to the rotation. He's posted a 6.82 ERA over 31 2/3 innings.
During his recovery, the Padres worked extensively with Diaz to adjust his mechanics. The one-time Brewers prospect has big-time velocity, but the club felt too much of that derived exclusively from his arm. So they altered his delivery a bit to better incorporate his lower half.
"He's made some good adjustments," Green said. "Is he 100 percent there? No. It takes awhile for guys, but he's made some adjustments. His arm is alive."
After Thursday's off-day, the Padres will need six starting pitchers in five days, a product of their doubleheader against the Dodgers on Saturday. Right now, Diaz is the likeliest option to slide into the rotation.
As for Coleman's demotion, it was more about roster management than anything else, and it's reasonable to think he'll return to San Diego shortly. Coleman batted .227/.268/.455 in 27 games for the Padres, while also serving as their best defensive infielder.
"It was nothing about how he had played," said Green. "I'd actually, frankly, like to start Dusty today. But we've got some arms in the bullpen that have been taxed pretty heavily."