White Sox rookie Lucas Giolito took the mound on Sunday looking to be a different guy than he was in his first start of 2017.

In his debut against the Twins, he gave up four runs on three home runs; each homer came on a fastball. The curveball, Giolito said after the start, wasn’t there the way he’d have liked and it forced the young right hander to throw the heater.

In Sunday’s start against the Tigers, which saw Giolito go 7 scoreless innings and give up just three hits, three walks and strike out four, the curveball seemed to have much better shape and command. All in all, it was a big step forward for the young man who started the season reworking his mechanics in AAA. What’s more, the White Sox won their 51st game of the year by beating the Tigers, 7-1.

Especially poignant in Sunday’s game was Giolito’s final inning of work. After retiring Miguel Cabrera and Nicholas Castellanos to start the inning, he walked Mikie Mattock, gave up a single to John Hicks, and walked Jacoby Jones. It was the biggest trouble-spot of the day.

Manager Ricky Renteria came out to talk with his young charge and, instead of pulling him for a fresh bullpen arm, left him in the game to finish his work.

The next pitch to Jose Iglesias went over the fence in left for a grand slam.

At least, that’s what the umpires thought. Iglesias had pounded a ball, that’s for sure, but it went foul–just a few feet left of the foul pole. The call was reversed, Giolito hung in and got Iglesias to ground out, and the White Sox kept the shutout alive.

It would be Giolito’s last inning but the final lesson learned might have been the most powerful.

As the Sox finish out the month of August and head into September, Giolito’s starts (as well as Reynaldo Lopez’ once he’s off the disabled list) are the can’t-miss games for the Sox. As they develop and begin to mesh with Carlo Rodon, the White Sox could get a large piece of the puzzle figured out.