Loup's first pitch was the turning point as Gregorio Petit hit a solo homer over the left-field wall to overshadow another strong start by J.A. Happ in the Blue Jays' 3-1 loss at Minute Maid Park.
"When was the last time you've seen three balls barreled off of Loup in a row," manager John Gibbons rhetorically said after his club's winning streak was snapped at six games. "He's a groundball guy, but he didn't get any groundballs."
With the game tied at 1, Loup entered the game in the eighth inning. The first pitch he threw was a 92-mph fastball that got too much of the plate and Petit hit a line-drive to left for the first homer of his big league career.
Loup allowed another run in the eighth after Jose Altuve hit a double to the gap in left-center field, advanced to third on a stolen base and eventually scored on a sacrifice fly by Robbie Grossman. It was the first time Loup allowed a run since July 9 vs. the Angels, which also marked the only other time he surrendered a homer this season.
"I threw two pitches, the next thing you know, I give up a home run and a double," Loup said. "We've been playing great baseball, I owe it to the guys on the field behind me to run them down ... I guess it just wasn't my day. [We'll] get out there and just go get them tomorrow."
The relief appearance spoiled what was an otherwise impressive night on the mound for Toronto. Happ continued his recent run of success by allowing three hits and two walks, while striking out six en route to another quality start.
Happ's only real difficulty came with two outs in the fourth inning. He had retired 11 consecutive batters at that point, but then he allowed an infield single to Chris Carter and issued a four-pitch walk to Matt Dominguez.
Houston's Jesus Guzman made Happ pay for the momentary lapse with a bloop single to center field for the Astros' first run of the game.
That was the only run Happ allowed on the night. He has yielded three runs or fewer in four consecutive starts and has given up a total of four runs over 18 1/3 innings since the All-Star break. Happ battled some inconsistency earlier this season, but he has since become a pivotal member of the starting rotation.
"I feel strong, trying to get in some kind of groove out there and got some good results tonight, so I'll always take that," Happ said.
"I think the goal is to try to stay healthy and get out there. I felt like I could help contribute. Just trying to stay there and give this thing a good shot, these next two months."
Toronto got started on the right foot when Melky Cabrera and Jose Bautista singled in the first inning to put runners on the corners with one out. Dioner Navarro made it 1-0 with a sacrifice fly to left field.
Another golden opportunity was presented in the second when Danny Valencia doubled to put runners on second and third with none out. Toronto came up empty, though, as Munenori Kawasaki popped out, Ryan Goins struck out and Jose Reyes flied out to end the inning.
Astros starter Collin McHugh yielded the lone run, while scattering five hits and one walk over 6 1/3 innings with five strikeouts. Darin Downs and Jose Veras bridged the gap to closer Chad Qualls, who recorded his 12th save of the season.
"My command was a little bit off today," McHugh said. "I was actually talking to [catcher Carlos Corporan] about it. It kind of felt like smoke and mirrors at times. We had a good game plan. He was really good behind the plate pitching to my strengths ... A lot of credit goes to him and the staff for preparing us well. It was a battle today."
Toronto is now 11-4 and has yet to lose a series since the All-Star break. The Blue Jays have two more games remaining in Houston before heading home for series against the Orioles and Tigers.