CHICAGO -- Jordan Lyles didn't get the win in his major league debut, but he certainly made a big splash.
"That first inning I went out there and got the ball from the third baseman, I just stood on the mound and took it all in," Lyles said. "It's a once in a lifetime type of opportunity and I couldn't ask for anything better."
Lyles committed a throwing error in the eighth which cost him a chance to earn his first big league victory. He scattered five hits and struck out four. He gave up two runs, both in the eighth inning.
After a Geovany Soto leadoff double in the eighth, Lyles tried to gun down pinch runner Brad Snyder at third on Tyler Colvin's pinch-hit sacrifice bunt. The throw sailed off the tip of third baseman Chris Johnson's glove and into left field, allowing Snyder to score and tie the game at 1-1.
"I had my mind made up that I was going to go to third with it. I just dropped my arm a little bit and it tailed away from (Johnson)."
Lyles was starting in place of the injured Wandy Rodriguez, who is on the 15-day disabled list with swelling in his left elbow.
"He was throwing everything for strikes, keeping guys off-balance, throwing exactly how we saw him throw in spring training," Astros manager Brad Mills said. "He lived up to every expectation of every Astros fan, the management, the organization ... everything."
Cubs closer Carlos Marmol blew his third save of the season, allowing six runs in the ninth inning to send the Cubs to their fourth loss in five games.
Downs has four hits and four RBIs in 14 plate appearances as a pinch-hitter. He said it wasn't easy to get used to at first, but he's getting the hang of it.
"You get into the game real quick because your adrenaline is running," Downs said. "I've done it enough this year that I'm getting used to it. It's getting easier and easier to be mentally prepared for it."
Pence finished with three hits, extending his hit streak to 12 games. He's hitting .451 (23 for 51) over that span.
Fernando Rodriguez Jr.(1-0) got the final out in the eighth to earn his first career win.
Marmol faced seven batters and recorded just one out, a sacrifice bunt. He hadn't allowed a run in 13 1/3 innings before the blowup.
"It was a bad day. What can you do about it," Marmol said. "They swung at your best pitch (slider) and they hit it."
Zambrano settled down to retire the next 11 batters, including six by strikeouts. The streak was broken up by Lyles' first career hit, a soft single under the glove of first baseman Carlos Pena.
Wallace's home run was the lone blemish on Zambrano's outing. The righty allowed seven hits over eight innings and struck out seven.
Lyles ran into trouble in the fifth inning when Blake DeWitt's leadoff pop-up to shallow left field fell to the ground untouched in a moment of miscommunication between shortstop Clint Barmes and left fielder Carlos Lee. DeWitt was credited with a double and advanced to third on a Tony Campana sacrifice bunt.
But the righty promptly struck out Soto and Zambrano to end the threat. Zambrano broke his bat over his knee out of frustration after going down swinging.
Lyles, the youngest active player in the Major Leagues at 20 years and 224 days, surrendered his first hit to Starlin Castro, the second youngest player in the majors. Castro, who turned 21 on March 24, tripled to right field in the first inning but failed to score. Lyles struck out Castro in his next at-bat.
Astros OF Jason Bourgeois (strained left oblique) took live batting practice Tuesday and is scheduled to play rehab games Thursday through Saturday with Triple-A Oklahoma City if all goes well. ... RHP Brandon Lyon (right biceps tendinitis and rotator tear) is scheduled to throw a simulated game Thursday in San Diego. ... Cubs RHP Matt Garza (elbow) is doubtful for a return this weekend at St. Louis, as the club initially hoped for. Manager Mike Quade said the team wants to play it safe and give Garza an extra side session. He will be able to start during the Cincinnati series June 6-8.