CHICAGO — The Houston Astros came into Chicago hoping to break one of their few slumps this season in a three-game series with the American League’s worst team. Instead, they leave the Windy City reeling after being swept by the White Sox.

Meanwhile, White Sox fans got a glimpse of a potential South Side superstar who had his first big moments for the team.

Rookie Yoan Moncada homered to tie the game in the ninth inning and then drove in the game-winnerwith a single in the 11th to lead the White Sox to 3-2 win Thursday night, completing an improbable series sweep of the AL’s best team.

The top White Sox prospect said his 11th inning single wass the first walk-off hit he’s had at any level.

“It was something indescribable,” said Moncada, speaking through a translator. “My feelings, all my emotions were through the roof when I hit that ball and then when I was running the bases. It was something unique.”

In the 11th, Leury Garcia led off with a single past diving second baseman Jose Altuve that was then bobbled by right fielder Josh Reddick, with Garcia advancing to second on the error. Altuve dove again for Moncada’s hit off Francis Martes two pitches later but could only watch as the White Sox celebrated moments later near his spot in the infield.

“We’re not in a great place right now, we obviously had a tough trip to this city,” Astros manager A.J. Hinch said. “We’ll move on to the next city and get ourselves right again.”

Earlier, Moncada homered in the ninth with one out against Astros closer Ken Giles for his second career home run.

“A star is born,” White Sox manager Rick Renteria said. “He’s taking some nice swings.”

It was the third blown save of the season for Giles, who has converted 22.

“I threw a good pitch,” Giles said. “I looked the video, right on the outside corner, right on the black. I have to tip my cap to him. He put a good swing on it and drove it the other way. You can’t really be mad at it.”

Martes (4-2) took the loss after striking out all three batters he faced in the 10th inning, and then allowing the two singles in the 11th.

David Holmberg (2-3) got the last out of the 11th to earn the win. Carlos Rodon threw his third straight quality start without earning a win.

Rodon, a left-hander, tied a career-high with eight innings pitched, striking out four and allowing two runs on nine hits. Jake Petricka, Tyler Clippard, Brad Goldberg and Holmberg combined to hold the Astros scoreless over the last three innings.

Houston right-hander Brad Peacock struck out five and gave up one run and seven hits in 6 1/3 innings.

Jake Marisnick hit a home run and Marwin Gonzalez added an RBI double for the Astros, who have lost seven of their last nine games.

The Astros (71-43) still have a comfortable lead in the AL West but need to return to their early season form.

“It’s frustrating,” Giles said. “We’ve had a lot of success early and haven’t really had bumps in the road. Right now, we’re going through it and trying to find ourselves again. But we’ll get it together as a team again and find ways to win.”

Down 2-0, Chicago’s Yolmer Sanchez drove in Avisail Garcia on a fielder’s choice in the sixth inning.

The Astros bullpen wiggled out of two jams before Giles blew the save in the ninth.

Chicago got the tying run to second base in the seventh, but Chris Devenski relieved Peacock and struck out Moncada and got Jose Abreu on an infield pop out.

Luke Gregerson allowed the first two runners to reach in the eighth inning, but struck out Sanchez and Tim Anderson and then got pinch-hitter Alen Hansen to ground out.

But Moncada and the White Sox didn’t let the third opportunity pass. The rookie has provided a spark for the White Sox, mired in last place in the AL Central at 44-68.

“I had a chance to watch Moncada in Triple-A and tell you what, it was something special,” Rodon said of his teammate, who came over as the centerpiece of a December trade with Boston for ace Chris Sale. “He’s got a good bat. Just a special player, man.”

STARTING STREAK

Nicky Delmonico singled in the sixth inning, becoming the first White Sox player since at least 1913 to reach base safely in each of his first nine career games.

MORE MISCUES

Anderson, the White Sox shortstop, committed his 23rd error when he misplayed a routine ground ball by Gonzalez in the fourth inning.

The shortstop had gone 19 games without an error, but leads the majors with 23, seven more than Detroit’s Nicholas Castellanos, who has the second most errors.

Anderson started a double play on the next batter, J.D. Davis, to end the inning.

TRAINER’S ROOM

Astros: Hinch said he doesn’t expect any of his eight players on the disabled list to travel to the team’s weekend series at Texas.

White Sox: Third baseman Matt Davidson (bruised right wrist) said he plans to swing a bat on Friday and hopes to return from the 10-day DL when the team travels to Los Angeles next week for two games with the Dodgers.

UP NEXT

Astros: The Astros will open Friday in Texas with RHP Charlie Morton (9-4, 3.78 ERA) taking on Rangers LHP Cole Hamels (6-1, 3.59).

White Sox: Kansas City comes to town for a three-game series, starting Friday with Royals LHP Danny Duffy (7-7, 3.48) taking on RHP Reynaldo Lopez, who is making his season debut.