CHICAGO -- Ben Zobrist was praising how Nicholas Castellanos goes about his pregame routine during batting practice. The veteran utility man was describing how Castellanos has infused a different kind of mentality and energy in the clubhouse for a Cubs team aiming for October.

As Zobrist spoke with a group of reporters, following the Cubs' 6-1 victory over the Mariners on Tuesday night, faint music began to grow in volume until the notes and beat started to drown out the veteran's words. It was Castellanos, carrying a portable stereo with him back into the locker room, where the outfielder realized he disrupted the interview.

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"My bad, guys," Castellanos said.

"There he is right there," Zobrist said with a grin. "I'm talking about you right now."

There has been plenty of talk about what Castellanos has done for the Cubs since coming over from the Tigers via trade at the July 31 Deadline. He has, unquestionably, been the motor for Chicago's lineup. Castellanos was at it again on Tuesday with a three-run homer, but this night was not just about the North Siders' newest cult hero.

No, this evening was about multiple sources of energy that the Cubs hope can help power a memorable September.

The evening included Zobrist's return to the starting lineup and leadoff spot after his nearly four-month hiatus. He saw a pile of pitches, ignited two rallies and set the tone atop the order. The night also featured the comeback of catcher Willson Contreras, who was activated from the injured list before the game after a month-long absence. Naturally, he belted a homer in his first at-bat.

"That gave me chills," Contreras said. "It was a special moment for me."

The cherry on top was a mammoth homer from Kyle Schwarber, who watched his seventh-inning shot soar to the top row of the right-field bleachers. The left fielder now leads the Cubs with 33 homers on the season and has posted a 1.106 OPS dating back to Aug. 1.

All of this happened on a day when the Cubs were without Kris Bryant (a late scratch due to a right knee issue) and Javier Baez (out with a jammed left thumb). And it backed a six-inning performance by Jon Lester, who dodged traffic and escaped three bases-loaded jams.

"That just speaks on how talented this clubhouse is from top to bottom," Castellanos said. "If somebody steps out, somebody else steps in."

When Zobrist stepped into the batter's box in the first inning -- marking his first at-bat for the Cubs since May 6 due to his time away to tend to a personal matter -- the Wrigley Field crowd offered him a rousing standing ovation. He stepped out quickly, but gathered himself and got back to work, not wanting to make more of the scene than necessary.

"It was warm, it was nice," Zobrist said. "But I was trying to get on with the at-bat and get going. I need to get past this moment and just be focused on the team."

The Cubs have missed his professional approach at the top. On the season, Chicago entered Tuesday with a .282 on-base percentage and a 70 wRC+ out of the leadoff spot. Against Seattle, Zobrist showed why manager Joe Maddon values the way he goes about forcing pitchers into the strike zone -- a trait the Cubs have lacked on the whole.

Zobrist saw six pitches in his first at-bat and then seven more in a third-inning walk, which later led to a run on a sacrifice fly by Castellanos. In the fifth, Zobrist executed a perfectly-placed bunt single up the third-base line. Two batters later, Castellanos ripped a pitch from reliever Wade LeBlanc into the right-center seats for his three-run shot.

"The at-bats were good. The focus was great," Maddon said of Zobrist. "He was very eager before the game in a good way. It was nice to see that. It's nice to see that at-bat at the top of the batting order -- the patience, the accepting of the walk, et cetera."

Contreras offered a perfect summation of what Zobrist's return means to the Cubs.

"He's a role model -- a role model to follow," said the All-Star catcher. "For me, he's a huge example to look up to. He's going to help us a lot, only by watching him going through his [routine], how professional he is. He's just amazing."

Like Zobrist, Contreras also raved about the energy that Castellanos has brought to the room and on the field. Consider that the Cubs posted a .252/.325/.460 slash line as a team in August, but those rates drop to .239/.317/.425 if you remove all the production from Castellanos' bat that is baked into those statistics.

In discussing Castellanos before the game, Contreras said he plans to "support his fire" down the stretch. The catcher also prides himself on being a spark plug for the Cubs. And Baez -- once he rejoins the fold -- offers much of the same infectious intensity.

Given what is on the line for the Cubs, Maddon is hoping all of this breathes more life into an offense that can make or break the team's October aspirations.

"We should be full go. They're all energetic players," said the manager. "That's what we need. I've talked about [how] September provides its own energy. Listen, we're in a race. There's no reason to show up and not feel that way, but these are the guys.”