CLEVELAND -- Watching Gavin Williams work against an overmatched A’s lineup on Sunday, it was easy to begin looking ahead to dream about his potential on the October stage. The big right-hander with overpowering stuff is the type of pitcher any team would love to lean on in the postseason.

“You can kind of see the panic in a lot of the hitters,” outfielder Steven Kwan said. “They’ve got to cover a bunch of different shapes and pitches. I think that's when he's at his best, is when the hitters are feeling really uncomfortable.”

The Guardians have work to do, but Williams got them one step closer to punching their postseason ticket on Sunday. He struck out nine over seven innings, allowing just three hits and one walk, to lead the Guardians to a 1-0 win over the A’s at Progressive Field.

Cleveland completed a three-game sweep in its final home game of the regular season. The Guardians (81-75) moved to 1 1/2 games ahead of the White Sox (79-76) for first place in the AL Central, pending the outcome of Chicago’s rain-delayed series finale against the Tigers. 

The Guardians also now have a three-game cushion on the AL West-leading Rangers (78-78) for the No. 2 seed in the AL -- and the first-round bye that would come with it. The next time they play in this ballpark, it could be a postseason game with Williams on the bump.

“That's the biggest goal,” Williams said. “Everybody wants to play in October, and that's what we're striving for every year.”

The White Sox hold the tiebreaker over the Guardians after winning the head-to-head series (7-6), which means Cleveland has to finish with a better record to win the Central. The Guards took care of business this week with a 5-1 homestand that included a series win over the South Siders.

The homestand also helped the Guardians eclipse 2 million in attendance at Progressive Field for a third straight season, which is the club's longest such streak since 2000-02. Williams gave the home crowd a lot to cheer for on Sunday, following a two-hour, five-minute rain delay.

The only real threat against Williams came after Zack Gelof and Donovan Walton hit consecutive singles to open the second inning. He worked around that traffic, and by the end of his outing had reassumed the AL lead in strikeouts (244), surpassing Dylan Cease’s 239.

Williams has a 1.44 ERA in 25 innings over four starts in September. 

“Just unbelievable,” manager Stephen Vogt said. “He takes the ball, [throws] seven strong and did his job. He was outstanding yet again today.”

The A’s (61-95) are well under .500. Any team can win on any given day in the big leagues, but this realistically was a series the Guardians had to win. Vogt was encouraged by how his club did so:

• In a 5-3 win on Friday, Joey Cantillo pitched six strong innings as a bulk pitcher out of the bullpen. José Ramírez and Travis Bazzana each hit a home run to help erase an early  3-0 A’s lead.

• In a 12-6 win on Saturday, the Guardians had 15 hits and seven extra-base knocks. They overcame an early 2-0 deficit.

• Sunday, Williams’ masterpiece combined with two scoreless innings by relievers Hunter Gaddis and Cade Smith helped hold up the lone run, which Ramírez scored after he reached on a double in the fourth.

In short: The Guardians won in diverse ways, which is crucial in the postseason.

“That's what I love about this team, is we have no idea how we're going to win on any given day,” Vogt said. “But we're going to find a way to do it.”

The job is far from complete. The Guardians’ six-game road trip against the Red Sox and Royals stands between them and a third consecutive division title. The White Sox have six games next week vs. the Royals and Rockies.

On paper, the series in Boston is perhaps the most daunting. The Royals and Rockies are well under .500, whereas the Red Sox clinched a postseason berth on Sunday. But Cleveland has to keep stacking up wins over the final week, no matter its opponent, as it has during a 12-7 start to September. 

That continues on Tuesday at Fenway Park.

“One day at a time,” Vogt said. “We can only control today. Let's go 1-0 every day and let's worry about tomorrow, tomorrow, because here we are one week to go, six games to go. We're right in it and we have a great opportunity in front of us.”