By Rob Rains

Neither Tommy Pham nor Magneuris Sierra know how long they will be on the Cardinals, but however long this opportunity lasts, they intend to make the most of it.

The two outfielders were called up from the minor leagues last week because of injuries that sent Stephen Piscotty and Jose Martinez to the disabled list and kept Dexter Fowler out of the lineup for six games.

That created playing time for Pham and Sierra, and all they have done is light a spark under the first-place Cardinals.

They did it again on Saturday against the Chicago Cubs at Busch Stadium as they each went 2-for-3, with Pham driving in two runs and Sierra one, to lead the Cardinals to a 5-3 victory.

In the eight games he has played since being promoted from Triple A Memphis, Pham is hitting .387 and seven of his 12 hits have gone for extra bases.

“When you are playing these good teams you have to be at your A game,” Pham said. “A team like Chicago, we know how good they play us. I want to contribute any chance I get.”

Pham has had stints with the Cardinals in the past, with limited success, but he believes there has been a difference this time since he joined the team.

“It’s vision, it’s mechanical, I’m trying to chase less and be more in the zone and when I get a good pitch to hit, I’m trying not to miss it,” he said. “I felt like last year at the end of the season I got in trouble because I was chasing more and wasn’t doing a good job hitting the fastball.

“Opportunities tend to create themselves, that’s kind of how this industry works. I’m just trying to make sure I’m ready.”

Manager Mike Matheny has been more than pleased with both how well Pham and Sierra have filled in for the injured players.

“I truly believe it’s a vision thing,” Matheny said of Pham. “He’s constantly working with whatever he has to do to see the ball. He puts some great at-bats together, nice to see whatever he had to do to make those adjustments. It sounds simple enough but it can be very complex. He continues to have an impact around here.”

Pham drew a leadoff walk against Jon Lester in the third, stole second, went to third on a throwing error by catcher Willson Contreras and scored on a suicide squeeze bunt by Carlos Martinez.

In the fourth, his RBI single followed a homer by Jedd Gyorko, his seventh of the season, which gave the Cardinals a 3-1 lead. He then doubled in another run in the sixth off reliever Pedro Strop and scored on a single by Sierra.

Sierra, called up from Class A Palm Beach because he was the only outfielder on the 40-man roster who was not in the majors, also had a single in the fourth as part of his 2-for-3 day. Sierra has at least one hit in all five games he has played since joining the team last Sunday, and the Cardinals have won all of those games.

Sierra is 8-for-20 in his five games.

“He’s unflappable,” Matheny said. “He’s going to be tested, the longer he’s here, the more the league starts figuring him out. It’s nice to have a player like that here. He’s got a lot more in there. He’s got a lot to learn but he’s conscientious and he wants to learn.”

Worth noting: Jhonny Peralta is expected to begin a rehab assignment at Memphis on Sunday. He played three games last week at Palm Beach, going 2-of-8 … Sierra got the start in right field, the first time he had played anywhere but center field since July 1, 2014, when he started the second of two games that season in right field in the rookie level Gulf Coast League …. Sierra replaced Randal Grichuk, who was 1-of-13 in his career against Lester. This was the first game this season Grichuk did not play. He had been the only Cardinal to play in the first 34 games of the season … Saturday was Michael Wacha’s scheduled day to pitch, but he won’t pitch again until next Friday, a 12-day span since his last start on May 7. The team wants to give him extra rest when the opportunity arises because of the problems he has had in the past with a stress reaction in his shoulder.

Looking ahead: Adam Wainwright will get the start in the series finale on Sunday while Jake Arrieta will start for the Cubs.

Follow Rob Rains on Twitter @RobRains