CLEVELAND -- As Astros manager Dusty Baker assessed what went wrong Sunday afternoon against Guardians ace Shane Bieber, one pitch in particular stood out in the 5-0 defeat at Progressive Field.

“Our young players are having trouble with that slider, which most young players do,” Baker said. “He has one of the top sliders around, so that’s not a very good combination.”

Bieber used his slider to induce 10 of his 21 outs in his seven-inning outing, which included nine strikeouts -- four of which came via the slider -- and just three hits and one walk allowed.

The Astros’ lineup was without three top hitters in second baseman Jose Altuve (who took a planned off-day) and shortstop Jeremy Peña (who was out due to illness). Yordan Alvarez also remained on the injured list with right oblique discomfort.

Peña was replaced by Grae Kessinger, who was called up from Triple-A Sugar Land on Monday and played in just his second MLB game.

But the youth -- which included four rookies in Kessinger, Corey Julks, César Salazar and Yainer Diaz -- joined Houston's veterans in struggling to handle the job against Bieber’s breaking ball.

“It’s the hardest thing for most young hitters,” Baker said. “Most times, when a guy in the Minor Leagues can get his slider over and has a decent fastball and command, he’ll probably be in the big leagues. He won’t be in the Minor Leagues for long.

“[Bieber is] a former Cy Young guy. He doesn’t have the velocity he once had, but he still has good command of all his pitches -- especially his slider.”

The younger players in the lineup did manage to discover some success against Bieber, though, on a day when the Astros mustered just six baserunners off the 2020 American League Cy Young Award winner.

Houston's best scoring opportunity happened in the fifth inning after a leadoff double from Diaz, who advanced to third after Kessinger tallied his first Major League hit on an infield single. The Astros were unable to send Diaz home, though, after Mauricio Dubón ran into tough luck, hitting a two-out ground ball up the middle to Andrés Giménez.

The second baseman was already running to the bag because Kessinger was attempting to steal on the play, so he easily stepped on the base before Kessinger arrived.

From there, Bieber returned to cruise control. He retired the Astros in order in the sixth inning and didn’t flinch when a one-out error allowed Diaz to reach base again in the seventh, setting the next two batters down in order.

“He was mixing his cutter and slider, and [he] was able to throw it off his fastball,” Kessinger said. “He was just hitting his spots all day.”

The Guardians also roughed up Astros right-hander Brandon Bielak for a season-high five earned runs in five-plus innings, which boosted his ERA to 3.96 through seven starts this season since he replaced the injured José Urquidy in the rotation.

Bielak allowed two home runs -- a 388-foot, two-run slam from Giménez in the second inning and a 425-foot solo shot from Josh Bell in the fourth inning -- and back-to-back doubles and a walk in the sixth inning before he was pulled from the game.

“He was in a situation where he was finding it hard to play,” Baker said. “He was throwing strikes, but if you throw it over the heart of the plate, that's the easiest pitch to hit. He just had a tough day in the zone.”

The loss completed a marathon stretch for the Astros with 17 games in 17 days. They went 9-8 in that stretch and went 2-5 on their seven-game road trip.

“You lost some tough games,” Baker said. “When you lose some tough games, that chips away at you. You knew that was going to be a tough part of the schedule.”