Clase, 21, made his Major League debut on August 4 after skipping the AAA level, going 2-3 with a 2.31 ERA in 21 games for the Rangers to finish out the season.
The move ends Kluber's nine-year tenure in Cleveland, in which he was a two-time Cy Young victor and three-time All-Star with a career ERA of 3.16.
The Cleveland Indians are in the final stages of trading pitcher Corey Kluber to the Texas Rangers, according to ESPN. As they move into their new stadium, the Rangers are expected to continue making moves, too.
Kluber is set to be paid $17.5 million for the 2020 season, with an $18 million club option for 2021.
Kluber is a former American League Cy Young award victor and will be heading to the Rangers to bolster their rotation. Progressive Field in Cleveland was a tough place to pitch, but it wasn't as bad as Globe Life Park, the Rangers' home ballpark last season. The Rangers' signings of Kyle Gibson and Jordan Lyles added additional depth behind incumbent veterans Mike Minor and Lance Lynn.
Kluber has been one of the best pitchers in baseball for the majority of his career.
The Indians know Kluber better than anyone, and they settled on what looks on the surface to be an unbelievably light return, which suggests they may not expect him to have much left in the tank.
Kluber's fastball averaged 94.6 miles per hour in 2014 and was down to 92.4 in 2018 and 92.3 last season. That's just 46 batters faced and his curveball remained an elite strikeout weapon, but his overall strikeout rate has fallen from 34.1% in 2017 to 26.4% to 22.6%. You can't go into 2020 expecting Cy Young-caliber Kluber, although this is far from a Felix Hernandez situation.