PHILADELPHIA -- The shortcomings of the Astros’ roster configuration means manager Joe Espada will have to dig deeper into his toolbox as his team tries to hold onto the lead in the American League West over the final five weeks of the regular season.

On Monday night at Citizens Bank Park, a pair of rookies -- infielder Shay Whitcomb, who was starting at second base, and reliever Bryan King -- delivered in big spots before the Phillies outlasted the Astros, 3-2, in 10 innings in the series opener at Citizens Bank Park between a pair of division leaders.

Whitcomb’s two-run double in the fourth inning off Phillies starter Zack Wheeler put Houston ahead, 2-0, but that was the Astros’ only hit with runners in scoring position (they finished 1-for-10). Meanwhile, King struck out cleanup hitter Alec Bohm to end the seventh and strand runners at first and second base.

“I thought we played well,” Espada said. “We were one hit away from winning that game. That's what happens. You play these types of teams and everything is close -- every play matters, every pitch matters, every at-bat matters. You turn the page because you've got another one tomorrow.”

The Astros have lost five of seven games since winning 11 of 12 from Aug. 6-19, which helped them open up a five-game lead in the AL West. That lead was still 4 1/2 games entering Monday’s rematch of the 2022 World Series, which was won by Houston.

The Astros have been without Kyle Tucker for nearly two months, they rested All-Star second baseman Jose Altuve (they are in the midst of playing 18 consecutive games without a day off) until using him as a pinch-hitter in the ninth and they have only seven relievers because they’re using a six-man rotation. And one of their best relievers, veteran Ryan Pressly, is on the injured list.

King, who made his Major League debut on June 23, recorded one of his biggest outs in the seventh. Espada showed tremendous trust in King when he brought him into a tie game to face Bryce Harper, who he walked to put runners on first and second. But King then struck out Bohm looking on a fastball to end a 10-pitch at-bat.

“Going after Harper is priority one, but in this game, you have to be ready to face anybody,” King said. “That was the situation and the plan was to try to go attack him and see if we can get him out.”

Bryan Abreu pitched a 1-2-3 eighth and closer Josh Hader blew away three in the ninth on three punchouts. But Hader allowed the automatic runner to score in the 10th on Harper’s sharp single to right field.

“Our bullpen has been outstanding throughout this whole entire road trip, giving us a chance to win some games,” Espada said. “We’re leaning hard on those guys. They’ve been really, really good -- reliable. We haven’t been able to get that big hit to seal the win.”

The bottom of Houston’s batting order has been the team’s weakest link for much of the season, and with Tucker out, the Astros’ offense can’t afford to not come through in the clutch. The Astros are 14-23 in one-run games, which is one of the reasons they haven’t put the division away yet.

Houston is 2-3 on its difficult road trip to Baltimore and Philadelphia -- a pair of teams expected to contend for the World Series. The Phillies packed 39,627 fans into the ballpark on Monday, and the crowd erupted on Harper’s walk-off hit.

"They’re a good team,” Espada said. “There’s a reason why they're leading in their division. It’s a well-rounded team, from starting pitching, the bullpen and a good offense. I expected that from this series. There are going to be some close games.”

As the playoffs approach, the Astros will need more young players to keep answering the bell.

“I think there were a couple of moments in the last series in Baltimore that had similar energy,” Whitcomb said. “Being able to go to these parks and experience the different environments has been a real experience.”