CHICAGO — Wearing a sleeveless T-shirt with “WE ARE GOOD” in big block lettering, Jake Arrieta looked at ease while he made himself a sandwich and mingled with teammates Sunday morning.

The bearded ace of the Chicago Cubs was one cool customer heading into Game 3 of the deadlocked NL Division Series on Monday night. He also was the biggest challenge for the St. Louis Cardinals, who insist they will be ready for the first playoff game at Wrigley Field in seven years.

“We’ve gone up against a number of teams and a number of pitchers where everybody kind of ruled us out and said you can’t do this or that, and I think this team has responded well in the past,” Cardinals Manager Mike Matheny said.

The past includes a history of postseason success. It also includes a victory over Arrieta in May, but that was long before he went on one of the most dominant runs ever seen.

Dating to a four-hit shutout against Minnesota on June 21, Arrieta is 17-1 with a microscopic 0.81 ERA. The stretch includes a no-hitter against the NL West champion Los Angeles Dodgers, and a five-hit shutout at Pittsburgh in the wild-card game last Wednesday.

“I’ve been through a lot in my career, and the failure that I’ve gone through makes me really appreciate the moments of success much more,” said Arrieta, who looked as if he might be on his way out of baseball when he was traded from Baltimore to Chicago in July 2013.

“I’ve had some pretty dark times in this game in my career, you know, but I was dedicated to getting over the hump, to putting in the time, the effort, making any adjustments necessary to get to this point.”

Arrieta had 236 strikeouts in 229 innings on the way to a 22-6 record.

A return to form for Michael Wacha would help the Cardinals. Wacha, who was the MVP of the 2013 NLCS as a rookie, led St. Louis with 17 wins this year, but struggled to a 7.88 ERA in five September starts.

The last time Wacha was on the mound in the playoffs, he served up a game-ending homer to Travis Ishikawa in Game 5 of the 2014 NLCS at San Francisco.

“Just excited for this opportunity this year, being a part of this amazing team and looking forward to seeing what we can do in this postseason,” Wacha said.