Gerrit Cole is heading to Houston after spending the past five seasons (2013-2017) in Pittsburgh.
Martin, who is now rated as Houston's 15th-best prospect according to MLB.com, was selected by the Astros in the eighth round of the 2013 draft.
Cole, 27, went 12-12 with a 4.26 ERA, 196 strikeouts and 55 walks while making a career-high 33 starts in 2017. He was the No. 1 overall pick in 2011 by Pittsburgh and is twice a first-round pick as he was taken 28th overall by the Yankees in 2008.
Chris Archer, Michael Fulmer, Matt Harvey and other prominent starters have had their names tossed around in recent swap speculation.
On Friday, Cole avoided arbitration by agreeing on a one-year deal worth $6.75 million. "But as we looked at how we position ourselves to be better as an organization, we felt this was the right move to get these three players that are major-league ready with 15 years of potential contribution combined versus the two Gerrit had remaining".
Luhnow characterized Cole's acquisition as having a "significant cost" because the Astros "love" the four players they're giving up.
Moran, 25, had strong numbers at Triple-A last season but that came in the hitter friendly Pacific Coast League.How his 18 homers in 338 at-bats will translate to the major leagues remains to be seen.
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Musgrove could take over Cole's spot in the rotation.
Outfielder Andrew McCutchen is scheduled to become a free agent after next season.
Musgrove did appear in 38 games for the Astros last season, posting a 4.77 ERA with 98 strikeouts in 109.1 innings.
Injuries checked Cole to 21 starts in 2016, but he rebounded a year ago and was one of just 15 pitchers in the majors to work 200-plus innings.
Moran will now get an opportunity to be the Pirates' starting third baseman, with David Freese sliding into a platoon role at third and first base.
Alex Bregman didn't have to tweet much.
"Colin Moran. projects to be a quality left-handed hitting third baseman with developing power", said Huntington. "We just happen to have someone in front of him".