With a bad weather report for Sunday, Roberts wanted to have a multi-innings reliever on hand in case starting pitcher Kenta Maeda had a short start or one delayed by rain.
With Maeda coming off three consecutive outings of four innings, the Dodgers needed a long reliever for coverage. Ravin pitched two scoreless innings on Saturday and Ross Stripling, who had been the club's long reliever, was optioned to OKC on Friday after yielding home runs in back-to-back outings.
Although Stewart has been starting for OKC, Roberts said his initial Dodgers role would be long relief.
Stewart -- ranked by MLBPipeline.com as the Dodgers' No. 7 prospect -- began the season on the disabled list after developing right shoulder tendinitis in Spring Training. Stewart has made three starts at OKC and one rehab start at Rancho Cucamonga this year, with a combined ERA of 5.19 but also 14 strikeouts in 8 2/3 innings.
Stewart began last year at High A, but raced through the system to make five Major League starts for the Dodgers.
Ken Gurnick has covered the Dodgers since 1989, and for MLB.com since 2001.