And atone he did.
Johnson hit his first grand slam in the first inning, and the Astros beat the Cardinals 8-2 behind a solid start by right-hander Bud Norris to win a fifth consecutive game for the first time since late 2010.
"Bud's a guy that every time he pitches, we're excited because we know if we scratch a couple of runs across, Bud's going to be competing out there for us," Johnson said. "I let him down in the first inning and he gave me a little pep talk after that on the bench, saying 'let's go; forget about it,' so I picked us up and he took care of the rest."
The victory earned the Astros their second consecutive home series win with a game to spare. The last time the Astros won five straight was Aug. 22-26, 2010.
Norris (2-1) continued his dominance of the Cardinals, allowing just one unearned run on three hits over six innings to improve to 7-2 with a 2.16 ERA in 11 career starts against them.
"We had a good gameplan, and I stuck to it, Norris said. "Made some good pitches, made some bad pitches.
"We know that's a good hitting team. I stuck to the gameplan and everything worked out pretty well."
It was nothing the Cardinals hadn't seen before.
"Same thing he has always done," Cardinals manager Mike Matheny said of Norris. "We can't really put our finger on it or else we would fix it.
"It's just some guys you have a hard time with, and we couldn't string anything together."
Left-hander Jaime Garcia (2-2) was charged with six runs on four hits in six innings for the Cardinals, who lost their season-worst third straight. Garcia walked four and struck out two for his second loss in as many starts.
Jed Lowrie hit a two-run home run in the eighth off Cardinals reliever J.C. Romero for the final margin. It was originally ruled an RBI double, but after a review the umpiring crew changed it to a homer after seeing the ball bounce off the railing above the yellow line over the left-field wall. It was Lowrie's fourth home run of the season.
Johnson more than made up for a fielding error in the top of the first by taking Garcia deep on an 0-2 pitch with two outs in the bottom half to give the Astros a 4-1 lead. The slam came in Johnson's second start since he went 4 for 4 with two home runs and a career-high six RBIs in Wednesday's 8-1 win to sweep the New York Mets.
"The problem was the walks," Garcia said.
Astros manager Brad Mills was equally pleased with the at-bats that preceded the grand slam.
"I think the way we went about is. the patience to load the bases with three walks and then (Johnson) was able to get a ball up in there and hit the grand slam," Mills said.
The Cardinals got on the board first with Carlos Beltran's RBI single to right field that scored Rafael Furcal, who singled to lead off the game and reached third a batter later when Johnson failed to secure a ground ball.
"Bud made a good pitch, had two strikes on (Jon) Jay, and I booted it," said Johnson, who went 2 for 4. "I really, really wanted to do something good in that at-bat, and he threw a slider out over the plate, and I was able to get it over."
Maxwell, who started at center field in place of Jordan Schafer, put the Astros ahead 5-1 with an RBI double in the fourth and Norris added a run with a sacrifice fly.
After limiting the Cardinals in the first, Norris was dominant the next three innings, at one point retiring eight in a row. He allowed three walks in the sixth, including one to David Freese with two outs to load the bases, before getting catcher Yadier Molina to ground into a forceout to end the inning.
"The last couple games, unfortunately with two outs I've been giving up bad hits -- not necessarily bad pitches, but I need to bear down better," Norris said. "I had that opportunity today with Yadier and got that big ground ball, and it speaks volumes to me and my growth going forward."
"I had to ask to stay out there, and (Mills) had the confidence in me to stay out there, and I appreciate that."
Norris, who walked four and struck out four, got his first win since April 19 at Washington.
Matt Holiday hit an RBI single off Astros reliever David Carpenter to cut the lead to four before Lowrie went deep.
Beltran was back in the starting lineup after pinch-hitting in Friday's 5-4 loss to the Astros. Beltran missed the previous two starts with a sore right hamstring. ... Astros RHP Rhiner Cruz was scheduled to pitch for Triple-A Oklahoma City on Saturday night and again Monday, Astros manager Brad Mills said. Cruz was placed on the disabled list retroactive to April 24 with an ankle sprain. ... Johnson's grand slam was the second by the Astros this season. Schafer hit one April 22 against Los Angeles. ... After the game, the Astros recalled RHP Aneury Rodriguez from Class Triple-A Oklahoma City. He will start Tuesday.