First-pitch balls led to falling behind in the count, which led to runs, which led to a bad day at the ballpark for the Astros.

And with their offense being shut out for the first time this season, it led to a runaway win for the A’s, who stretched their lead atop the American League West to 4 1/2 games with a 6-0 wipeout of the punchless Astros on Monday night at the Coliseum.

• Box score

A’s starter Chris Bassitt twirled seven impressive innings, allowing just seven singles, against an Astros lineup that’s without starting second baseman Jose Altuve and third baseman Alex Bregman. Houston was held without an extra-base hit for the second time this year and shut out for the first time since Game 1 of the 2019 AL Championship Series against the Yankees.

“It’s been a tough stretch for us, but we have to keep positive,” said Astros starting pitcher Cristian Javier, who allowed two runs in five innings. “We have to keep focused on doing our jobs and make sure we turn this thing around.”

Like the Yankees, the Astros are reeling and putting themselves in danger of having to fight for a playoff spot in the final three weeks. That would have seemed unthinkable even a week ago, but the Astros have lost five in a row to start their 11-game road trip. And the Mariners are only two games behind them for the postseason slot allotted for the second-place finisher in the AL West.

“You don’t look behind you,” Astros manager Dusty Baker said. “Somebody might be catching you and trying to overtake you, but we can’t look behind us. Nothing lasts forever. I think we had another streak of five games [lost in a row last month] and then we reeled off eight [wins] in a row. You can’t be afraid of somebody overtaking you from behind.”

But in front of them lies a hungry A’s team that is looking to increase its lead in the division with four games remaining in this series, including Tuesday’s doubleheader. With just over two-thirds of the season in the books, the Astros’ streak of three consecutive AL West titles is in peril.

“We wanted to start this series hot, which we did,” Bassitt said. “But we want to increase the gap between us and Houston. This is a massive series, and we don’t have a lot of games left. It’s a great opportunity to give us some wiggle room, and tonight was just the start of it.”

Baker’s club has been besieged by injuries, though Bregman is expected to return for Tuesday’s doubleheader. A young staff that’s seen 10 pitchers make their Major League debuts this year, including Javier, has struggled with command and walks.

“It’s something that we’ve got to live with until they get the experience and get their acts together as far as not walking people,” Baker said.

Javier walked three batters and allowed three hits and two runs, but a 34-pitch second inning -- which included an RBI double by Tony Kemp and a solo homer by Sean Murphy -- meant Baker had to go to his young bullpen sooner than he wanted. Houston’s bullpen gave up four more runs and has allowed 17 walks and 18 earned runs in 20 1/3 innings (7.97 ERA) in the first five games of the road trip.

“We had to take Javier out because he had a bunch of pitches,” Baker said. “He was getting behind a lot with his breaking ball and he’d come with the fastball. We had too many deep counts. Every time we walked somebody, it seemed like they scored. That’s their game plan over there.”