Diaz will undergo arthroscopic surgery after tearing the lateral meniscus on his right knee, Kevin Acee of The San Diego Union-Tribune reports.
Diaz suffered the injury during a bullpen session Saturday. He's expected to return before the end of April but will almost certainly open the season on the injured list. The 24-year-old will lose out on his chance to be a part of the Opening Day bullpen but still could spend a good chunk of the season on the big-league roster after recording an excellent 35.3 percent strikeout rate in 18.2 innings of relief last season.
