O’Day’s injury should be Duquette’s signal to acquire veteran lefty reliever

The news that sidearmer Darren O’Day will be out for at least 15 days with a rotator cuff strain in his right shoulder is obviously a big blow to one of the best bullpens in baseball.

O’Day is the unit’s leader, but he’s also one of the club’s most effective relievers versus left-handed hitters, despite being right-handed (a .229 average against lefties this season).

Countless times while O’Day was out for nearly two months with a hamstring strain, Orioles manager Buck Showalter talked about how the absence really stung because O’Day could do the work of two pitchers. And that assisted Showalter in his constant bullpen juggling.

During that time, Brad Brach filled in at the set-up role in the eighth and was splendid. But, subsequently, right-hander Mychal Givens was called on to pitch the seventh more often, and his struggles versus left-handed hitters are well-documented.

When O’Day returned in late July, Orioles executive vice president Dan Duquette talked about how getting him back and signing Logan Ondrusek (a right-hander advertised as good versus lefties, too) out of Japan was like acquiring two relievers in the trade market.

But O’Day is gone again. He had a cortisone shot in his shoulder Saturday, and Showalter told reporters in San Francisco that he thinks the injury may not require longer than a 15-day stay. So O’Day could be ready to come off the disabled list by Aug. 28.

The Orioles weathered the storm without O’Day in June and July, so what’s another couple weeks?

The difference, of course, is that this is crunch time. The Orioles have basically one and a half months left, and every game, every inning, is crucial. And the bullpen, like most in August, is showing some signs of fatigue.

Consider all of that, and the O’Day injury makes the Orioles’ vulnerability versus lefty hitters late in the game more glaring.

Rookie Donnie Hart has flummoxed left-handers so far (they are just 1-for-9 against him), but it’s tough to count on someone with such little experience in a pennant race. Ondrusek is back in the minors after allowing four hits and two walks while facing 10 left-handers.

Givens has gotten better recently, but lefties are still hitting .355 against him on the season.

Lefties Brian Duensing and T.J. McFarland will eventually be back from injury, but, again, it’s tough to count on them now.

So this is when Duquette should strike and boost the bullpen for the stretch run. His trade checklist last month was right-handed-hitting outfielder, lefty starter and lefty reliever. He got two of those in Steve Pearce and Wade Miley, but found the cost for a lefty reliever – some teams were asking for Dylan Bundy – was too steep.

That may still be the case. But a team like the Colorado Rockies, who were hanging onto lefty Boone Logan while they remained in the race last month, are further out of contention now.

The Orioles checked in on Logan in July, and they also kicked the tires on San Diego’s lefty duo of Brad Hand and Ryan Buchter, and Minnesota’s Fernando Abad (who ultimately was dealt to Boston).

Trading this month gets a little trickier since players have to pass through trade waivers first, but it’d be surprising if at least one solid lefty didn’t get through.

If so, Duquette should pounce. He may not have the deepest farm system at his disposal, but it should be solid enough to land a lefty specialist in return.

Yes, O’Day may be gone for only 15 days, but neutralizing lefties has been a priority all year.

Now it appears even more necessary.