Keuchel and McCullers are coming off injuries that ended their 2016 seasons prematurely and will enter the '17 season looking to be healthy anchors to the rotation. Altuve, of course, is perhaps the game's best hitter and coming off his second batting title in three years.
All three know there is a lot riding on this season -- and their performances -- which is why they've been at Minute Maid Park several days a week working out together with other teammates, a list that has included Marwin Gonzalez, Alex Bregman, Brady Rodgers and David Paulino, among others.
"I've been here the whole offseason," said McCullers, who is living in Houston this winter so he can have the team's strength coaches and athletic trainers at his disposal. "I've been in there with Dallas and Altuve since the start of November. I feel like we've already had a mini Spring Training and just want to be around the full team again and be healthy going into this year ready to go."
McCullers, 23, began 2016 on the DL with right shoulder soreness and ended it battling a sprained elbow, going 6-5 with a 3.22 ERA in 14 starts in between. He's healthy and throwing off flat ground three times a week at Minute Maid Park. He's on a normal progression like he would be in any other offseason.
"It's a go-as-you-feel," he said. "If I feel good one day -- like yesterday, I threw a little bit further than what I thought I was going to because I felt good. I know my body more as I get older and I'm hoping to get off the mound three or four times before spring."
Keuchel, 29, recently admitted he battled fatigue all of last season. Coming off an American League Cy Young Award campaign in '15, he went 9-12 with a 4.55 ERA in 26 starts last year before missing the final month with shoulder inflammation. Like McCullers, he's throwing off flat ground with the hopes of getting on the mound in February.
"I've been telling some of the guys it actually feels weird to feel good," he said. "It's the first time in a long time that I feel 100 percent, and that's just exciting."
Keuchel said he's hoping to be able to handle a big workload next season in anticipation of the Astros making a deep playoff run. He's also still considering pitching for the U.S. in the World Baseball Classic, but only if he's 100 percent and in the latter rounds of the tournament.
"Just the way I felt last year, just the body didn't recover," Keuchel said. "It was kind of like I was pushing through it all year."
"It seems like we have the team we want and the new pieces and the guys we have are ready," Altuve said. "We have a great team. It seems like this team is going to go all the way through, and we've got to do everything that we can do to get ready and prepare for the season."
Brian McTaggart has covered the Astros since 2004, and for MLB.com since 2009. Follow @brianmctaggart on Twitter and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.