NEW YORK — Triston Casas, whom the Red Sox took with the 26th overall pick of the amateur draft this month, is out for the season after having a torn ulnar collateral ligament in his right thumb repaired Thursday.

The Sox made the announcement Friday.

Casas, 18, was injured Monday afternoon while diving for a ball during a Gulf Coast League Game in Fort Myers, Fla. The Sox sent him to Boston, and Dr. Matthew Liebman did the surgery at Newton-Wellesley Hospital.

Casas is expected to be ready for next season. He could participate in the Instructional League in September, but the team is sure to be cautious with a prospect they signed for a $2.55 million bonus.


The power-hitting third baseman was 0 for 4 with a walk and two strikeouts in two games.

Peter Abraham can be reached at pabraham@globe.com. Follow him on Twitter @PeteAbe.