MEXICO CITY -- The biggest reason the Astros have struggled in April is the health of their pitching staff. Six starters have already spent time on the injured list this season, including five at the same time.

That forced Houston to call up some young arms who weren’t quite ready, putting more pressure on a bullpen that was adjusting to new roles. It was an imperfect storm that put first-year manager Joe Espada in a tough spot.

Slowly but surely, the Astros’ arms are getting healthy. Justin Verlander returned from the IL on April 19 and has pitched well, and left-hander Framber Valdez made his return on Sunday, logging five strong innings in an 8-2 win over the Rockies in the Mexico City Series finale at Estadio Alfredo Harp Helú.

“I thought he threw the ball well,” Espada said. “The first couple of innings, command wasn’t there, but he settled in. He threw some really good changeups and he gave us five innings. That’s exactly what we wanted out of him.

“Super encouraging to see him, the way he threw the ball and seeing him healthy. That was great to see.”

Kyle Tucker hit a towering solo homer in the first inning off Rockies starter Austin Gomber, and Jose Altuve wowed the pro-Astros crowd with a solo homer in the third inning to put Houston ahead, 3-2. Jeremy Peña added a homer to lead off the fourth to help the team to its first series sweep of the season.

“We had a conversation as a team [after getting swept by the Cubs on Thursday] and we said this is going to be our new beginning,” Espada said. “We know we haven’t played to the caliber of team that we are and we’re going to just leave that in the past and must move forward from here.”

Valdez, pitching for the first time since April 2, threw 71 pitches -- the Astros were targeting 70-75 -- while allowing five hits and no walks to go with six strikeouts. Valdez was scratched from his April 8 start against the Rangers with a sore elbow, but didn’t need to make any Minor League rehab starts.

“I went 15, 20 days without pitching,” Valdez said. “When I was out there, I definitely felt a lot of pressure and it took the first two innings for me to be able to settle down, just continue pitching.”

Having Valdez return to pitch in Mexico City -- where the ball flies at an elevation of 7,350 feet -- provided him a chance for success. His career 63.5 ground-ball rate leads MLB pitchers since 2018 (minimum 500 innings) and Valdez relied on his changeup and curveball to keep the ball out of the air. The Rockies had three flyouts, in addition to a sac fly.

“We all know that the altitude here is very different than it is in Houston, but I was able to just execute my pitches when I needed them -- my sinker, my curveball and as well utilized my changeup,” Valdez said.

Next, the Astros are hoping to get starter Cristian Javier (neck) back next weekend after he threw in the bullpen Sunday. Then there’s Jose Urquidy, the Mexican-born starter who threw in the bullpen on Sunday -- the day after visiting Mexican president Andrés Manuel López Obrador in his office -- and is in line to return from his forearm strain in mid-May.

Houston still wants to get Hunter Brown on track and has high hopes for rookie Spencer Arrighetti, but having Verlander, Valdez, Javier and Urquidy back at the top of the rotation is what the club had hoped for to start the season.

Entering Sunday, the Astros’ 4.95 ERA from their starting pitchers was 28th in the Majors and they were 25th in innings pitched by their starters.

“You get two All-Star-caliber pitchers back in the rotation, it’s nice to have,” reliever Ryan Pressly said. “Obviously, you never want to lose those guys, but injuries happen and that's when you need the next guy to step up. … It gives the guys in the bullpen a little bit more confidence knowing that those are your horses and when they go out there and throw 80, 90 pitches and take you into the sixth inning, it gives you a chance to win.”