PITTSBURGH — Pirates infielder David Freese got a two-year contract extension Monday, then made the final out on a baserunning blunder in a game hours later.

Doug Fister pitched seven scoreless innings of three-hit ball, Teoscar Hernandez hit a two-run homer and the Houston Astros beat the Pirates 3-1 on Monday night.

Ken Giles got his fourth save despite allowing Freese’s RBI single in the ninth. Freese was thrown out at second base when he tried to advance on an overthrow.

“You can’t be out there at second base,” Pirates manager Clint Hurdle said. “You’re two runs down. That probably was some emotional baserunning. The only way it works is if you’re safe.”

Houston won its fourth straight game and Pittsburgh lost its fourth in a row. Both teams are competing for wild-card spots.

Freese signed a two-year, $11 million contract prior the game that takes him through the 2018 season. The 33-year-old infielder will make $6.25 million in 2017 and $4.25 million in 2018. There’s a $6 million club option for 2019 or a $500,000 buyout.

Freese signed a one-year, $3-million contract as a free agent March 11 and is hitting .276 with 12 home runs and 50 RBIs in 108 games. The eight-year veteran has made 59 starts at third base and 26 at first base.

“It’s always good to be wanted and the Pirates made that clear when they offered the extension,” Freese said.

Hernandez connected off fellow rookie Jameson Taillon (3-3) in the fifth inning after A.J. Reed’s leadoff walk. It was the third home run for Hernandez, who was called up from Triple-A Fresno on Aug. 12 to make his major league debut.

Taillon made his seventh consecutive quality start since being activated from the disabled list July 19. He pitched eight innings, allowing two runs and four hits with a career-high eight strikeouts.

“Leadoff walk — that’s always bad,” Taillon sad. “I don’t know what the statistics are, but it seems like they score a lot. I fell behind the next guy and he cranked a pitch out. That’s baseball. If you fall behind and make a mistake, they make you pay.”

Alex Bregman, another Astros rookie, hit his fourth homer in the ninth inning off Neftali Feliz.

Gregory Polanco had a pair of doubles and scored Pittsburgh’s lone run.

Fister struck out six, walked one and retired 11 of the first 12 batters. He had allowed nine runs and 11 hits over nine innings in his previous two starts.

“I was just kind of mixing things up,” Fister said. “(Catcher) Jason Castro had a good game plan and it came down to executing it.”

Trainer’s room

Pirates: RHP Tyler Glasnow (right shoulder soreness) pitched three scoreless innings and threw 57 pitches Monday night in his second rehab start with Double-A Altoona, allowing two hits while striking out six and walking three against Harrisburg in the Eastern League.

Bell gets chance

Rookie 1B Josh Bell, who was recalled from Triple-A Indianapolis on Saturday, made his second straight start. Hurdle said the 24-year-old switch-hitter will see the majority of playing time in place of slumping 1B John Jaso.