ST. LOUIS – Thursday’s 4-3 Pirates' loss to the Cardinals at Busch Stadium could best be summarized by three breaking pitches. The first two were cutters by Mitch Keller that left the yard, a two-run shot by Paul Goldschmidt and a sixth-inning blast by Brendan Donovan that served as the winning run in the series rubber match.

Then there was the slider Hunter Stratton threw in the eighth to Donovan. It dropped in for a strike, but even before he caught catcher Yasmani Grandal’s toss back to the mound, Stratton was calling for assistant athletic trainer Tony Leo and exited with a shoulder injury.

The severity of that injury is not yet known, and manager Derek Shelton summed up the decision to remove him by saying, “he was tight, so we’re not going to risk it.” But if Keller’s pitches made an impact on a loss, losing Stratton could hurt a bullpen that doesn’t have much depth to spare at the moment.

While Stratton’s season ERA is 4.26, that’s been greatly inflated by three bad outings where he surrendered 13 of his 15 earned runs this season. For most of the year, he’s been solid in a variety of middle relief roles, whether it’s to keep a game close or protect a lead in the sixth or seventh.

The Pirates need guys like that. While David Bednar has gotten back on track after his shaky start and Colin Holderman has been terrific as the setup man, the team is lacking proven, reliable middle relievers. It’s also experiencing a shakeup of late.

There are already two new faces in the Major League bullpen: lefty Justin Bruihl and right-hander Dennis Santana. Bruihl signed as a free agent earlier this month, and Santana was claimed off waivers Tuesday. The duo got the other five outs for the bullpen Thursday.

Relying on new faces also indicates there aren’t a lot of other options at the moment. Lefty Jose Hernandez, a main player in last year’s bullpen, was designated for assignment Tuesday to make room for Santana after struggling for most of the year.

Ryder Ryan was optioned for a fourth time this season Thursday, but given that the only other healthy pitchers on the Pirates’ 40-man roster are starters Braxton Ashcraft and Daulton Jeffries, he could be coming right back to Pittsburgh.

There are also new faces with Triple-A Indianapolis after right-handers Luis Cessa and Jake Woodford signed Minor League deals earlier this week, giving them some veterans who can throw innings if necessary, but without an open spot on the roster, adding them would come at the cost of losing a player.

If necessary, there’s a little bit of quantity. This group needs quality, too.

Some of the young relievers on the Major League team are on a good roll. Carmen Mlodzinski is looking more like his 2023 form of late, and Kyle Nicolas opened eyes Wednesday when he struck out the first five Cardinals he faced. Nicolas found some success by positioning himself closer to the center of the pitching rubber, which catcher Henry Davis theorized created a better angle to get the ball over the plate, which has been the main challenge with him.

“Obviously, those couple games [leading up to Wednesday] didn't go how he wanted, but it's closer stuff,” Davis said Wednesday. “It's some of the best stuff I've caught.”

The Pirates could really use a couple arms to step up, regardless of whether Stratton needs to hit the injured list. They did their part this series, picking up after less than stellar starts from Keller and Bailey Falter. The team is in no position to be wasting quality starts from their rotation if they want to become a major player in the playoff race, and part of that includes continuing to do a better job protecting leads.