ST. LOUIS -- Dodgers manager Dave Roberts had a simple answer when asked what he expected from starter Hyun-Jin Ryu before Monday’s game against the Cardinals.

“To get a lot of outs,” Roberts said.

Ryu may have been on his way to delivering on his manager’s prediction before leaving the 4-3 loss to the Cardinals in the bottom of the second with a left groin strain. It's similar to the injury that landed Ryu on the injured list from May 3 to Aug. 15 last season.

“It was different from the pain I felt last year,” Ryu said through an interpreter. “It was more of a precautionary measure to come out of the game. So compared to the left groin injury I had last year, right now I feel better.”

His early exit left the bullpen, already taxed from logging 13 1/3 innings over the weekend in Colorado, to pick up the final 6 1/3 innings against the Cardinals.

The load proved too much as the Cardinals snapped Los Angeles’ five-game winning streak.

“To go [almost] seven innings and to give up two runs against that ballclub here, I thought we did a great job,” Roberts said. “All these guys threw the ball really well and gave us a chance to win.”

Joe Kelly had trouble finding the strike zone in the sixth, walking one and falling behind the first four batters he faced. His wild pitch allowed Paul Goldschmidt to score, breaking a 3-3 tie.

Roberts had wanted to stay away from Kelly, who earned the win Sunday in Colorado. But Kelly called into the dugout after Ryu went down and said he was ready to go.

“Obviously you look at the stuff, and the stuff is really good,” Roberts said. “And I certainly applaud him for calling down to the dugout and wanting to take the baseball after last night. ... I think that right now some pitches are just finding some outfield grass, and [he's] just not making some pitches that he will make.”

Enrique Hernández's baserunning error in the top of the sixth thwarted a Dodgers rally. With Max Muncy on third and Hernandez on second with one out, Hernandez took off on a line drive to center hit by Russell Martin. But Cardinals center fielder Harrison Bader made the catch and easily doubled Hernandez off second.

“He just thought that Bader was a little bit deeper, and it was a ball that was kind of softly hit and he just thought he had a bead on it and didn’t expect Bader to come up with it,” Roberts said.

It was the second mental mistake by Hernandez in as many games. On Sunday, he forgot how many outs there were and was unable to turn what would have been a likely inning-ending double play.

An A.J. Pollock double gave the Dodgers a 2-0 lead in the first inning, but the lead was erased in the bottom half by Marcell Ozuna's two-run homer.

Trainers came to the mound after Ryu delivered his first pitch to Miles Mikolas with two out and nobody on. Ryu threw just 34 pitches before exiting. He gave up two runs on two hits, one walk and one strikeout.

Roberts expects to place Ryu on the injured list Tuesday and call up another arm to bolster the Dodgers' bullpen.

“I just don’t think right now with where we are with the 'pen, we just don’t have the luxury to carry a guy who isn’t going to pitch for another four days,” Roberts said. “I think something needs to happen.”

Power outage
The Dodgers went homerless for the first time this season. They entered the game with 24 homers in their first 10 games, tied for the third most by any team in their first 10 games in Major League history.

It took the Dodgers 26 games last season to hit 24 home runs.

"I think Busch Stadium does a good job of that as well, but it was also me sticking to my game plan, trying to keep them off balance,” Mikolas said. “Not necessarily missing bats a whole lot, but just trying to miss that barrel enough to keep those fly balls in the park."