PHILADELPHIA -- The Phillies' faith in their pitching depth is being pushed to its limits.

They potentially have lost right-hander Seranthony Domínguez for the season after he suffered an ulnar collateral ligament (UCL) injury in his right elbow Wednesday in San Diego. Dominguez could be headed for Tommy John surgery, although he plans to receive a second opinion.

He is the seventh Phillies relief pitcher on the injured list, joining right-hander Tommy Hunter (strained right forearm), David Robertson (right elbow soreness), Victor Arano (right elbow inflammation), Edubray Ramos (right biceps tendinitis), Pat Neshek (strained right shoulder) and left-hander Adam Morgan (strained left forearm).

Ramos could rejoin the Phillies next week. Neshek and Morgan could return during the road trip through Atlanta and Washington from June 14-20. Hunter is scheduled to begin a rehab assignment in the next 7-10 days. Robertson could return sometime in July.

"While we are piecing it together right now, I think there is light at the end of that tunnel and sort of by the time we get to the end of the month, we will be back to fielding a pretty deep bullpen like we had intended for the year," Phillies general manager Matt Klentak said Friday afternoon at Citizens Bank Park.

Closer Craig Kimbrel just signed a three-year, $43 million contract with the Cubs on Wednesday. The Phillies had interest in Kimbrel, but only on a one-year deal. Asked if they would have pursued Kimbrel more seriously had Dominguez's injury popped up earlier, Klentak said: "Probably not. I don't know. We obviously didn't know.

"In the last couple years, we've signed several veteran relievers to two-year deals, but multiyear deals nonetheless. Each of them has spent time on the IL. There have been reasons why we signed those guys to try to bolster the bullpen, and I'm not saying we'd never do it again, but I do think we need to be mindful of the realities of relief pitcher health, especially multiyear commitments to veteran guys. The track record is not great. It doesn't mean you're never going to get a good one. Certainly there are going to be some good ones, and there are some good ones right now. But I do think we need to be very mindful of the realities of free agency when we're talking about multiyear deals for relievers."

Klentak said he does not believe the injuries are from overuse or a change in training and conditioning methods; they might stem from pitchers throwing harder and using more breaking balls.

"We also have to leave open the possibility that it's some combination of those things, and also maybe a bunch of stuff happened to us at once and it was bad luck," he said. "I'm not saying that it is bad luck, but it's certainly possible."

One way to bolster the pitching would be upgrading the rotation. Left-hander Dallas Keuchel agreed to a one-year, $13 million contract with the Braves. The Phillies never pursued Keuchel, preferring their internal options and believing there might be better fits in the future, if needed.

"I know we haven't been perfect in the rotation, but by and large our guys have gone out, taken the ball and kept us in games for most of the year," Klentak said. "There haven't been that many games where the starter was the reason we weren't in the game. Our rotation has been solid and they've been healthy. Again, that doesn't mean it'll be that way for the next four months. I'm very aware of how a baseball season can unfold, but right now we're comfortable with the guys we're running out there and the fact we have Cole Irvin in Triple-A. We have six of them right now."

Either way, the Phillies will continue to monitor the starting pitching and bullpen markets before the July 31 Trade Deadline.

Outfield update
The Phillies promoted Adam Haseley on Tuesday to replace Andrew McCutchen, who will miss the rest of the season because of a torn ACL in his left knee. Haseley had to be scratched from Friday's lineup because of soreness in his left hip flexor. He was available to pinch-hit and will continue to be monitored. Scott Kingery moved from third base to center field. Maikel Franco started at third base.

Outfielder Roman Quinn (strained right groin) continues to rehab in extended spring training. It is unclear, whenever he returns, if he will play center field over Haseley or if they will share time.

Roster moves
The Phillies activated right-hander Zach Eflin from the IL before Friday's series opener against the Reds. He missed his last start because of "mid-back tightness." The team also recalled left-hander Ranger Suarez and optioned right-hander Yacksel Rios.