Left-hander Jordan Montgomery, who was sent to the bullpen in August after a seven-start stretch in which he posted a 7.88 ERA, will return to the Arizona Diamondbacks' rotation against the Colorado Rockies on Tuesday.

Montgomery made four relief appearances for the Diamondbacks after the switch, producing one save and a 4.85 ERA during that stretch. However, with starter Ryne Nelson landing on the 15-day injured list due to right shoulder inflammation, Montgomery (8-6, 6.25 ERA) is returning to the rotation to make his 20th start of the season.

The Diamondbacks are currently in the thick of the National League wild-card race. Entering Tuesday's games, they hold the second of three wild-card spots, with just a one-game cushion over the New York Mets and two over the Atlanta Braves.

The injury bug has hit Arizona (83-67) hard lately. In addition to Nelson, the D-backs placed reliever Paul Sewald on the 15-day injured list on Sunday, retroactive to Thursday, because of neck discomfort on the left side. He would be eligible to return Sept. 27, which would give Arizona an extra arm for the final three games of the season.

Montgomery has fared well in two career starts against the Rockies, going 2-0 with a 3.09 ERA.

Field Level Media contributed to this report.