Lopez was optioned to the team's alternate training site Monday, Scott Merkin of MLB.com reports.
Lopez was battling for the fifth rotation spot, but was expected to serve as a reliever for the team even if he lost out on the role. However, he had a disastrous spring training, allowing 11 earned runs across 11 innings while surrendering three home runs and four walks. Lopez will likely pitch in the big leagues at some point this season, but he'll have to wait for injury or poor performance for his next opportunity.