The Arizona Diamondbacks activated right-hander Ryne Nelson from the 15-day injured list on Thursday after he recovered from right shoulder inflammation.

In other moves, the Diamondbacks recalled outfielder Alek Thomas from Triple-A Reno and optioned rookie righty Yilber Diaz and lefty Blake Walston to Reno.

Nelson, 26, has not pitched since Sept. 8. He experienced some shoulder discomfort during a throwing session on Sept. 14 and was placed on the injured list, retroactive to Sept. 11.

He is 10-6 with a 4.33 ERA, 34 walks and 125 strikeouts in 147 2/3 innings over 27 games (25 starts). In parts of three seasons with Arizona, Nelson is 19-15 with a 4.62 ERA, 86 walks and 237 strikeouts in 310 innings over 59 games (55 starts).

Thomas, 24, is batting .191 (18-for-94) with three homers and 17 RBIs in 37 games with the Diamondbacks this year.

Diaz, 24, made his major league debut on July 8 and was 1-1 with a 3.81 ERA, 12 walks and 19 strikeouts in 28 1/3 innings over seven games (four starts).

Walston, 23, made his big-league debut on May 1 and was 1-0 with a 4.42 ERA, 10 walks and 18 strikeouts in 18 1/3 innings over seven games (two starts).