ARLINGTON, Texas -- Texas Rangers right-hander Kohei Arihara needs shoulder surgery and is expected to miss at least 12 weeks.

Rangers general manager Chris Young said Saturday that Arihara has an aneurysm in his pitching shoulder. Dr. Gregory Pearl, a vascular surgeon, is set to repair the posterior circumflex humeral artery Thursday in Dallas.

"Dr. Pearl is one of the two best in the country for this procedure," Young said, "so we're very confident he will have a full recovery."

Arihara has been on the 10-day injured list since May 9, and left-hander Hyeon-Jong Yang has taken his place in the Texas rotation. Arihara threw a bullpen session Monday but felt discomfort in the middle finger of his right hand.

The diagnosis was made after an examination this week.

Texas signed Arihara to a two-year, $6.2 million contract as a free agent after he spent six seasons with the Hokkaido Nippon Ham Fighters of Japan's Pacific League. He is 2-3 with a 6.59 ERA in seven starts for the Rangers.