On this date two years ago, the Chicago White Sox were 64 games under .500 and headed toward the losingest season -- 121 defeats -- in the modern era of Major League Baseball.

Ahead of the opener of a three-game road set against the Chicago Cubs on Monday night, that futility seems like a lifetime ago.

After sweeping the Detroit Tigers over the weekend, the White Sox own a 5 1/2-game lead in the American League Central -- their largest cushion since winning the division in 2021. The surging club will be tested against its fellow contender and crosstown rival on Monday.

The White Sox won two of three games against the visiting Cubs in May.

Luis Castillo (4-9, 4.96 ERA) on Monday will make his third start for the White Sox since being traded from the Seattle Mariners on Aug. 1. The veteran delivered his best outing of the year on Wednesday, tossing seven scoreless innings, allowing just one hit, striking out a season-high 10 batters and walking two in a 5-0 win over the Cincinnati Reds.

The two-time All-Star has labored through a career-worst ERA, but the 33-year-old said hopes the return of his changeup will carry forward the momentum of his last start.

"It was about time for me to start having confidence in that pitch," Castillo said. "I haven't thrown it much before, but that was the plan -- to throw more changeups. And it was effective (on Wednesday). That's the result when you have confidence in your pitches, confidence in your plan, and we had a very good plan."

A rival of the Cubs when he pitched for the Reds, Castillo is 7-6 with a 3.60 ERA in 18 career games against the Cubs, who have lost consecutive games for the first time since July 9-10 after allowing 19 runs across back-to-back losses to the St. Louis Cardinals over the weekend. They enter the Monday contest firmly planted in the top National League wild-card spot.

Shota Imanaga (8-9, 3.74 ERA) will look to move past a disappointing last outing when he takes the mound for the Cubs. The 32-year-old left-hander allowed four runs on six hits across 4 2/3 innings on Tuesday, striking out five in a no-decision against the Washington Nationals. Chicago won 8-6 in a start that saw Imanaga fail to reach five innings for only the third time this year and allow three Washington home runs.

"He was a little off from the beginning," Cubs manager Craig Counsell said of Imanaga's last start. "You could just tell the command was not there. The misses were bigger than usual. In his mannerisms on the mound, you could kind of see it. But sometimes that's what you got, and you've got to work with what you've got."

Navigating an up-and-down third major league campaign, Imanaga said he will continue to make adjustments as his team enters the regular season's stretch run.

"I think the important part is thinking about what pitches the hitters are hunting on specific counts and not throwing those pitches," Imanaga said through a translator. "The first two home runs I gave up (against the Nationals), I threw the pitch they were trying to hit and I missed my location. The third one, that's hats off to the hitter. But I'm just trying to think about what pitchers they're looking at and trying to throw a different one."

Imanaga has allowed six homers across his past three starts, and the White Sox are a home-run-hitting club. They are first in the American League in runs with 594 and third in home runs with 164.

In two career starts against the White Sox, he's 0-1 with a 9.82 ERA.

As for the buzz surrounding the rivalry between the North Siders and the South Siders, the late-season meeting shapes up to be as competitive as any in recent history.

"It's exciting. I think it's great for baseball and great for the city," Cubs second baseman Nico Hoerner said. "We've always had great atmospheres playing the White Sox, regardless if we're having a good year, they're having a good year or either of us are struggling. Both teams have playoff hopes, and it just makes for a great series."