There are times this season where Marcus Semien has looked like an overmatched rookie. There are times where he has had the poise of a veteran.

Semien had the latter on display on Wednesday night.

The rookie got ahead in the count before he ripped a fastball for a game-winning grand slam in the seventh inning of a 6-4 White Sox victory over the Detroit Tigers in front of 23,451 at Comerica Park. The White Sox are in position for a series victory with a win in Thursday’s finale.

Semien’s drive made a winner of fellow rookie Andre Rienzo, who pitched 6 1/3 solid innings. It was also a big night for veteran Paul Konerko, who singled to start the winning rally. He had three hits and surpassed 2014 Hall of Fame inductee Frank Thomas to establish a franchise record with 3,950 total bases.

“Early on (Semien) had some rough at-bats and he just stays with it,” White Sox manager Robin Ventura said. “He continues to grind and fights off stuff and fights off a tough pitch and gets another one. He’s a good player. He’s a guy you like to see up there with guys on base.”

All three of Semien’s homers in 2014 have put the White Sox ahead in the seventh inning or later.

The infielder has had some bright moments in his second full month in the majors. He also has had some rough ones.

Three days after his bases-loaded triple put the White Sox over the top in Texas, Semien delivered again with his team trailing 4-2.

Konerko, who ended a 17 at-bat hitless stretch with a late single Tuesday, singled off reliever Evan Reed to start the seventh. One out later, Alejandro De Aza singled and Tyler Flowers walked to load the bases.