Owings struggled in his start Monday against the Padres, as he allowed eight runs on six hits over three innings to raise his ERA to 5.93 and drop his record to 6-9.
"It became pretty evident that we had to clear some things up with him," D-backs manager Bob Melvin said. "He was a key piece for us last year and I think he's going to be a key component for us going forward this year."
Owings' biggest issue was his command, which seemed to desert him after his first 10 starts of the year when he went 6-2 with a 3.73 ERA. Pitching coach Bryan Price diagnosed a flaw in Owings' mechanics in which his front shoulder flew open, which caused his arm to drag. That lowered his elbow and he ended up getting around the ball rather than on top of it so his pitches tended to run too much.
Figuring out what was wrong was the easy part. Correcting it in the bullpen was also not too difficult. Figuring out how to get it corrected once Owings took the mound, well that proved to be elusive.
"Some early first-inning work was good," Price said of the scoreless first inning Owings tossed Monday. "He just wasn't able to maintain it, especially once the ball got rolling and they got some guys on base. There's something going on. We weren't able to put our finger on it. We worked hard at it. It could certainly be simply the stress of added expectations. We're trying to win as many games as we can and he's a big part of it. We count on him."
The bullpen was not an option because it seemed unlikely that he would get regular enough work to iron out the problem.
"We can't put him in a long relief role and expect that two innings a week is going to get him back on the beam," Price said. "And more side work wasn't going to make a difference because his side work was fine. It's simply mechanical. Why is it happening in competition and not on the side? That's the question. The biggest challenge is how do you pitch without stockpiling more expectations and placing more pressure on yourself."
A stint in Tucson might be just what the doctor ordered. Owings, according to Melvin, was surprised when informed he was being optioned.
"Rather than look at it like it's a demotion for him it's more some time to clear his head and get down there and work on some things so he can get back here and help us," Melvin said.
Peguero appeared in two games for the D-backs earlier this year and allowed a pair of runs in three innings. In 41 games with Tucson, the right-hander was 5-4 with a 4.42 ERA.
With Owings' demotion, Yusmeiro Petit moves into the rotation and will start Saturday against the Dodgers.
Steve Gilbert is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.