ST. LOUIS -- Jon Lester had the grand majority of the 45,239 fans -- the first full-capacity sellout at Busch Stadium this season -- in his corner on Saturday night. But four of those had an enhanced importance.

His wife, Farrah, and their three kids have joined the 37-year-old as he primes to pitch in his 10th postseason and chase his fourth ring. That quartet in particular will be chief among his thinking process for next season, which would be the 17th of his decorated career if he opts to return. Decisions, conversations and future-weighing -- that’ll come when October ends.

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So there is a chance that Saturday’s 6-5 loss to his former Cubs might have been both Lester’s final start as a Cardinal and the final start of his career. Without any guarantee past the National League Wild Card Game on Wednesday, his possible last start was deflated by one pitch -- hit for a grand slam by Trayce Thompson in the fifth inning -- and Lester’s possible last pitch finished a strikeout.

But his team is worried about making sure he can throw at least one more.

“I'm not really worried about that right now,” Lester said when asked about his future. “I'm worried about hopefully having a deep run in the postseason. We’ll answer that stuff when the time comes.”

A deep postseason run is of special importance to Lester, not just because it would signify the Cardinals making a go at a World Series but because it would likely be a necessity for him to pitch in October.

With the strategy behind Wednesday’s tilt -- still to be determined whether it’s against the Giants or Dodgers -- Lester may not make the roster based on the game’s unique needs and his rest schedule. He would, however, line up for one of the first two games of an NL Division Series.

Should that hold true, then the last pitch of Lester’s career -- an at-bat after Thompson’s slam -- would have been a 88.4 mph sinker to whiff former teammate Sergio Alcántara, the 2,488th strikeout on his resume.

Also pitching behind Lester on Saturday was Kwang Hyun Kim, who is also on an expiring contract and who also is not a lock for the Wild Card Game roster. Kim did help his case, however, with a pair of scoreless innings.

“Those guys have been big contributors to our club,” said manager Mike Shildt. “KK did a fantastic job of settling that game down tonight.”

Of poetry on Saturday night was who was skippering the opposing dugout, Lester’s former catcher, David Ross. The Cubs’ manager said that the only way Saturday could have been more idyllic was if he was in place of Yadier Molina, catching his longtime batterymate one more time.

“I'm just glad I get to be here and watch it,” Ross said.

Ross was among the first to publicly congratulate Lester on his 200th win on Sept. 20 in Milwaukee. When the Cardinals ventured to Chicago next on that road trip, awaiting Lester in the Windy City was a dinner with his fellow 2016 World Series champion.

Such a rich history in Cubbie blue made the sight of Lester in Cardinal red hard to process when he was acquired at the Trade Deadline from the Nationals. But the three-time ring-bearer has done nothing but fit in with his new squad, one that’s caught fire down the stretch. He has been crucial to that success, with four of his seven wins on the year coming as a Redbird -- all of which have enhanced his opportunity to ride into the sunset with a deep playoff run.

What’s needed for that to happen is for another night like Saturday: a full Busch Stadium rocking at every turn -- from Lester’s first pitch to Harrison Bader’s leadoff home run and especially so during a three-run rally in the seventh for a temporary lead. Busch’s only remaining guarantee in 2021 is the regular-season finale on Sunday.

A win in either Los Angeles or San Francisco on Wednesday will be necessary to get Lester another start. In doing so, the Cardinals could pay back Lester for how he’s stabilized their rotation and make such an opportunity a distinct possibility.

“It's amazing to play in this place; this place rocks,” Lester said, “and I'm excited for postseason baseball here.”