Cueto (2-0, 1.78 ERA) is off to a great start with just five earned runs allowed in 25 1/3 innings and four outings. He's pitched into the seventh inning in all but one of his starts, and he beat the Cubs with a season-high seven strikeouts in 6 1/3 innings his last time out on Sunday, a 4-3 victory.
The Reds could use some length out of Cueto after starter Mike Leake lasted just 3 2/3 innings in a 6-4 loss Friday, in the opener of the three-game set.
"He has a nice slider, changeup. He elevates when he wants to and has something extra on his fastball," Cubs manager Dale Sveum said of Cueto. "Those kind of pitchers, it's very difficult to string a lot of hits together and runs unless you can pop a three-run homer or two-run double, something like that."
For the Astros, Lucas Harrell (1-1, 3.97) will try to rebound after giving up five runs in as many innings his last time out Monday, in a 6-5 loss to the Brewers. Harrell, also a right-hander, has never started against Cincinnati and has only faced the Reds once, last September when he gave up two runs in 1 1/3 innings.
"I didn't have command of my secondary stuff," Harrell said after the Brewers outing. "My sinker was really good, and I really got hurt most of the game with my offspeed stuff -- changeup on the home run to [Ryan] Braun, both triples were sliders down and away. I was real good inside. I kind of went away from the game plan a little bit, and that's where I got hurt."
Harrell looked best on the second day of the season, when he threw seven scoreless innings against Colorado in a 7-3 win.
The tide has turned quickly for the Reds, who had won five of six before losing the last two. Saturday marks the fifth game of a nine-game homestand for Cincinnati, and the fifth game of six on a road trip for Houston.
Astros: Lee exits with ankle sprain
A left ankle sprain forced Carlos Lee from Friday night's 6-4 win for the Astros. X-rays were negative and Lee is listed as day to day.
Lee was hurt going after a throw from third baseman Chris Johnson that got away.
Reds: Ondrusek on his game
Logan Ondrusek, a 27-year-old right-hander from Texas, has quietly gotten off to a stellar start. In 10 appearances and nine innings, he's yet to allow a run with six hits and four walks allowed. He's struck out eight.
"He had a good year last year," manager Dusty Baker said. "If we can keep going deep in the games with our starters and mix it up with our bullpen, when he's strong, he's very good. Last year at this point, we had to use our bullpen a whole lot more than we're using it now."
The next double for Cincinnati third baseman Scott Rolen will be the 505th of his career, which will tie him with Hall of Famer Tony Perez for 49th on that all-time list. Babe Ruth is 48th with 506 doubles.