Altuve's home run was off Kelvin Herrera (1-2) after Josh Reddick walked on four pitches.
He was activated May 27 and allowed one run and four hits over six innings to win at Texas.
McCullers faced the minimum number of batters the first five innings.
Lorenzo Cain broke up the no hitter with one out int he seventh and later scored on a two-out single by Mike Moustakas.
Astros manager A.J. Hinch said after Wednesday's game that Keuchel (9-0 with a 1.67 ERA) has "been sick for the last couple of days".
US AG to testify before Senate intelligence panel
Sessions said the Senate Intelligence Committee is most appropriate because it "has access to relevant, classified information". The Senate panel is investigating allegations of Russian meddling in the 2016 USA presidential election.
Lester lost at Wrigley Field for the first time in almost 13 months, while the Cubs dropped their second straight after winning a season-high five in a row.
Nationals 6, Orioles 1: Joe Ross had a career-high 12 strikeouts in a sparkling performance, and tired Washington breezed past visiting Baltimore.
Keuchel leads both lists and he was looking to become the fifth pitcher since 1987 to start the season with a 10-0 record.
The Royals held off an uprising in the eighth when the Astros scored three, the final two on an Escobar error with the bases loaded. The hard right came in the form of a four-run fourth inning.
Rockies 11, Indians 3: Rookie pitcher Antonio Senzatela hit a three-run double, and Mark Reynolds homered twice to drive in five runs in Colorado's win. St. Louis has lost seven in a row overall for the first time since 2013. Matt Carpenter hit a two-run homer in the eighth off Austin Brice. Martes was 0-2 with a 5.29 ERA in eight starts at Fresno.
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Many Democrats still blame Comey for Clinton's loss, leading Trump to apparently believe they would applaud him for firing Comey. Thursday's hearing brought Washington and other parts of the country to a standstill as Americans sat glued to their screens.
Elsewhere, the Baltimore Orioles edged the Pittsburgh Pirates 6-5, the Boston Red Sox overcame the New York Yankees 5-4 and the Los Angeles Angels beat the Detroit Tigers 5-3. "He gave me the green light, and I hit a good pitch". With such a sizable lead in the division, the Astros will probably be all right without Keuchel for a week-plus. They optioned RHP Kevin McCarthy, who did not allow a run in 6 1/3 innings, and OF Billy Burns to Omaha. It didn't match the shutout effort of his previous outing at Cleveland, but Vargas provided enough to keep the momentum after Tuesday's walk-off victory that ended the Astros' 11-game winning streak.
Closer Craig Kimbrel struck out five in 11/3 innings to seal the win.
Royals starter Jason Hammel allowed one run and four hits over seven innings. It is also worth noting that he has spent his entire six-year big league career in Houston.
Trailing 7-1 after 4 1/2 innings, the Royals appeared poised to drop their third straight game and fall to nine games under.500.
Garbine Muguruza hits out at French Open crowd
A new Grand Slam victor is set to emerge at the tournament as none of the women's players remaining made that. After losing 6-1 in the opening set, the Spanish levelled the score with a 6-3 win in the second set.