CHICAGO — Right-hander Brad Keller figures to hold down a role in the Royals rotation for several years. He'll be under team control until 2024. He'll turn 24 in July, and still has made just 32 starts in the majors.

As much potential as the Royals currently have stockpiled in the minors, Brady Singer, Daniel Lynch, Jackson Kowar and Kris Bubic remain a long way from being proven big-league commodities.

Meanwhile, Keller has had success in the majors. He's shown flashes of the ability and mentality to be a lead guy in a starting rotation. If and when that burgeoning youth movement sweeps over the starting rotation, Keller's presence and experience will be crucial.

The "ace" label placed upon him in spring training may prove to have been bestowed a bit prematurely — Danny Duffy has been the most consistent pitcher since coming off the injured list — but Keller's progression greatly affects the pitching staff's future outlook.

For that reason, his recent struggles were reason for moderate alarm. Since a victory on opening day, Keller was 1-5 with a 5.29 ERA in his next nine starts.

His last two starts have included signs of progress, however. On Tuesday night, Keller took a loss but went through a start without issuing at least three walks for the first time in two months (10 starts). That came on the heels of his win last Wednesday against the St. Louis Cardinals, which included seven scoreless innings before he ran into trouble in the eighth.

Tuesday against the White Sox, Keller gave up 10 hits. But he didn't give up an extra-base hit. Six of the 10 were ground balls. Keller relies largely on a sinker-slider combination.

"We had a good game plan going in," Keller said. "We got a lot of ground balls, and they kept squeaking by. A step over a step someway and we make some plays, but our infield was diving all over the place trying to get to the balls. Credit to them, but they just kept finding holes."

The most encouraging sign on Tuesday? In Keller's words, he "finally" filled up the strike zone with regularity. He'd struggled in recent starts to repeat his delivery, and he'd been firing pitches off-target.

"Way better (mechanically)," Keller said of Tuesday's start. "I pounded the zone. I got ahead of a lot of the guys and they just found a lot of holes tonight."

In Keller's sixth and final inning, he willed his way out of a potential game-breaking jam. The White Sox, leading 4-3, put runners on second and third and no outs.

Keller gave up a line-drive single up the middle and then a grounder deflected off the glove of second baseman Nicky Lopez and allowed the lead runner to go to third. The hitter advanced to second on the throw from the outfield.

But Keller bucked down and got back-to-back ground balls to third base with the infield drawn in, and an inning-ending fly ball to end the threat.

"He's such a ground ball guy, and he was getting his ground balls," Royals manager Ned Yost said. "We were just a foot out of (reach of) each an every one of them with a dive. I thought he threw the ball good. I thought he battled great.

"I thought it was a big inning for him in the sixth, second and third and nobody out on a ground ball that pushed when Nicky couldn't get it. He did a fantastic job of holding the fort right there to give us a chance."