BOSTON -- Red Sox pitcher Nathan Eovaldi took two steps toward the dugout when his 1-2 curveball against Houston Astros catcher Jason Castro landed in the glove of catcher Christian Vazquez close to the top-right corner of the strike zone. With two outs already in the ninth inning, Eovaldi momentarily believed he had stranded Astros shortstop Carlos Correa on second base and first baseman Yuli Gurriel on first, but plate umpire Laz Diaz never signaled the punchout that would have left the score tied at 2 heading into the home half of the inning.

Instead, the at-bat continued, with Castro eventually singling to center field, scoring Correa to give Houston a 3-2 lead in Game 4 of the American League Championship Series. Soon, the wheels fell off for Boston, which gave up seven runs in Tuesday's final frame as the Astros won 9-2 to tie the series at two wins apiece and push it to at least a Game 6, which will be back in Houston.

"I thought it was a strike, but again, I'm in the moment. I'm trying to make my pitches," Eovaldi said after the game. "I'm attacking the zone."

While Boston took issue with the call, the chance of Eovaldi's curveball being called a strike was 23%, according to ESPN Stats & Information research.

The borderline call characterized an evening marked by complaints about the strike zone. Diaz ended the evening with 23 missed ball-strike calls, according to ESPN Stats & Information, with 12 coming on balls thrown by Red Sox pitchers and 11 from Houston's hurlers. Diaz's night behind the plate marked the most missed ball-strike calls of any umpire this postseason.

Castro said that with the velocity and quality of Eovaldi's arsenal, he was looking for a pitch that wasn't at the top of the strike zone, where the 1-2 curveball ended up.

"Where that pitch started, I didn't think it was one I could pull the trigger on," Castro said. "It was a ball, then I was able to move on to the next pitch."

Red Sox manager Alex Cora said he had not watched video of Diaz's call before speaking with the media.

"I'm not going to get thrown out of this game, but we thought that pitch was a strike and he disagreed with us, but that's a tough job," Cora said. "I don't think -- yeah, it changes -- if it's a strike, it changes the whole thing, right, but I think we had chances early on."

Cora emphasized the difficulty of Diaz's job.

"I know Laz since our days in Miami, you know? He used to cover our games when I played at the University of Miami. Every Friday, he was the man in those games, so it's a hard job. I understand that. It's a hard job," Cora said.

Cora took stronger exception to a strike three called on designated hitter J.D. Martinez in the third inning on a 94.6 mph fastball thrown by Houston reliever Cristian Javier in a 3-2 count with Red Sox outfielder Alex Verdugo standing on first. The Red Sox manager ran out of the dugout to prevent Martinez -- who infrequently argues with umpires -- from getting ejected before confronting Diaz and needing to be restrained by third-base coach Carlos Febles.

Boston went 0-for-9 with runners in scoring position, leaving 11 men on base.

Red Sox starter Nick Pivetta came up short on words when asked about Diaz's strike zone.

"I'm not going to say anything," Pivetta said.

Eovaldi said the strike zone had an impact on the game's outcome.

"There's going to be those at-bats where I felt like our batters were being very selective up there," Eovaldi said. "They were having quality at-bats, and a 1-0 count that turns into a 1-1 or a 2-0 count, it changes the at-bat a lot."