CHICAGO -- The Chicago Cubs' new weapon more than likely will be put in the holster Friday during the opener of an interleague series against the Seattle Mariners at Wrigley Field.

Wednesday was simply a get-acquainted session for Aroldis Chapman. The newly acquired closer entered in the ninth inning and finished off the Cubs' 8-1 win over the Chicago White Sox.

On Thursday, it was strictly business. The left-hander entered in the eighth inning with two outs and a White Sox runner on third in a one-run game. He proceeded to strike out Melky Cabrera, and then he worked a one-two-three ninth en route to his 21st save of the year and first as a Cub.

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By pitching two days in a row, including the four-out save Thursday, Chapman isn't likely to be available Friday, however.

Going forward, Chapman's presence -- combined with that of late-inning pitchers Pedro Strop and Hector Rondon -- gives the Cubs an imposing relief force. Rondon spent much of the season as closer, compiling 18 saves.

"Especially with Chapman in the ninth inning, Stropy and me are more free to pitch in tough situations," Rondon said following the Cubs' 3-1 victory over the White Sox on Thursday. "We feel that's a strong bullpen right now."

The Cubs face Seattle right-hander Hisashi Iwakuma (11-6, 3.96 ERA) in Friday's series opener.

The 35-year-old veteran is 10-2 with a 3.69 ERA over his past 12 starts. The Friday start will be Iwakuma's second against the Cubs. He had a no-decision in an eight-inning effort on June 28, 2013.

The Cubs counter with lefty Jon Lester (10-4, 3.09 ERA). He is just 1-1 in his past six starts, but he boasts a 5-2 record and a 2.18 ERA at Wrigley Field this season. In his career against the Mariners, the Tacoma, Wash., native is 5-4 with a 3.52 ERA, although he has not faced them since 2014.

Mariners right fielder Nelson Cruz is expected back in the lineup after the team's off day Thursday. He sat out the Wednesday game in Pittsburgh after fouling a ball off his left shin on Tuesday.

Cruz's return is not good news for Lester. Cruz, who leads the Mariners with 25 home runs, has a .393 average with two doubles, a triple and three homers in 28 at-bats vs. Lester.

Like the Cubs, the Mariners have a new reliever in their bullpen this week. Right-hander Drew Storen was acquired from the Toronto Blue Jays for right-hander Joaquin Benoit late Tuesday night.

Storen made his Mariners debut Wednesday against the Pirates, allowing four runs in 1 1/3 innings.

"I grew up as a big Mariners fan," he told The (Tacoma, Wash.) News Tribune. "So it's kind of cool from the fan's standpoint in me. The team I grew up following. It's great."

Though Storen grew up in Indiana, he was attracted to the Mariners by the presence of future Hall of Famer Ken Griffey Jr.

"I was all in on Griffey," Storen told the News Tribune. "I had every teal jersey there was. I had the Mariners T-shirt and pillowcase during the playoffs and stuff. I was all in."

The Mariners, who are making just their second trip to Wrigley Field in franchise history, enter the series with a 10-3 interleague record, the best in the major leagues, ahead of the Boston Red Sox (8-3) and the Detroit Tigers (10-4).