HOUSTON – A ballpark with no fans and Zack Greinke can make for some terrific entertainment.

Greinke, the enigmatic veteran right-hander, took to calling his own pitches during the Astros’ 5-1 victory over the Giants on Wednesday night at Minute Maid Park by giving hand signals to catcher Martín Maldonado. And he could even be heard talking about changing up the signs, which was picked up clearly on television microphones.

• Box score

Greinke, who held the Giants to one run and seven hits in 6 1/3 innings for his first win of the season, said he began giving hand signals to Maldonado with a runner on second base earlier this year in an effort to speed up the game. 

“Today, there was a man on second base and it got all messed up and it took longer than I was hoping it would take,” Greinke said. “It’s 50 percent my fault and 50 percent Maldy’s fault. ... I don’t like taking a long time with a man on second base especially. I’m trying to find a way to speed that up. So far this year, it's been good. It got messed up today.”

While Greinke gave signs all game with a runner at second, there was confusion in the seventh inning. With Brandon Crawford on second base and Mauricio Dubón at bat, Greinke could be heard discussing the signs with Maldonado.

“Second set after one,” Greinke told Maldonado from the mound. “Second set after two,” he said moments later.

Dubón wound up flying out to center and Greinke was pulled after that. And it was Maldonado putting the game out of reach with a three-run homer in the sixth inning to push the lead to 5-1. His 12 RBIs are the most for a catcher in club history over the team’s first 18 games of a season.

“That was the difference in the game,” Astros manager Dusty Baker said. “We got excellent pitching. Zack, we were trying to take him to seven [innings] but that’s the most he’s gone [this year].”

When it comes to calling his own pitches, Greinke is not yet sure if he’s a fan of it, but Maldonado likes it.

“It’s good as a catcher not to have to put down or shake a couple of more times and slow the game down,” he said. “He’s a guy that likes to work quick.”

In Greinke’s previous start Friday in Oakland, he was also giving signs with his right hand to Maldonado and threw six scoreless innings. Whatever is going on with Greinke, it’s working. He’s allowed three earned runs and 15 hits in 18 innings in his last three starts.

“You probably won’t see another Greinke in your lifetime or mine, either,” Baker said. “This guy sure can pitch.”

Pitching mixup in Astros’ favor

The mound took center stage again at the end of the seventh when reliever Josh James ran all the way from the bullpen to pitch to start the eighth, only to find out he couldn’t. That’s because Brooks Raley, who got the last two outs in the seventh, had already tried to come back out of the dugout and ran onto the field, which meant he had to face at least one hitter.

Raley, acquired Sunday in a trade from the Reds, wound up pitching a 1-2-3 eighth and retiring all five batters he faced on the night. Baker said he gave Raley “knuckles” in the dugout after the seventh, but Raley didn’t know that meant he was done for the day.

“He doesn’t know me,” Baker said. “Next thing I know I look out there and he was the first one on the field and I said, ‘Oh man, you’re done.’ The umpire came out and said he had to face one batter since he crossed the line. ... It worked out great because he closed out the eighth very well.”

Raley thought Baker was giving him congratulatory knuckles.

“That meant something else,” he said. “Having been here a couple of days, I know now knuckles means ‘Have a seat.’”