The 24-year-old, who's 4-4 in his last 10 starts, has allowed three earned runs or less eight times in that stretch and pitched six innings or more eight times as well.
He tossed eight scoreless innings of an 8-0 Rays win over Seattle on Aug. 20, scattering six hits and striking out five Mariners.
Two subsequent starts have ended in two losses while the Iowa native gave up 12 hits and four runs in 13 innings with five walks and 11 strikeouts.
He's faced Baltimore five times in 34 major-league appearances and is 3-1 with a 2.63 earned run average across 27 1/3 innings with 11 walks and 15 strikeouts.
In Saturday's second game, B.J. Upton knocked in five runs with two doubles and the Rays doubled up the Orioles, 6-3.
Wade Davis (9-8) worked into the seventh inning to earn the win, giving up three runs on five hits while walking four and striking out five.
Davis was lifted after 6 2/3 frames with a man on base and the Tampa Bay bullpen didn't allow a hit the rest of the way. Kyle Farnsworth worked around a walk in the ninth to earn his 23rd save.
The Rays bounced back from Friday's loss and snapped a two-game skid. They are nine games behind Boston in pursuit of the American League's Wild Card berth.
Baltimore righty Jeremy Guthrie looks for a third straight quality start in his 20th career meeting with the Rays.
The Oregon native tossed seven innings of one-run ball in a 6-1 defeat of Minnesota on Aug. 24, then returned to allow three runs in six innings of a no-decision against Toronto six days later in a game the Orioles won, 6-5.
He is 6-9 with a complete game and a 4.18 ERA in 114 career innings against Tampa Bay, with 37 walks and 76 strikeouts.
Baltimore is 4-6 in his last 10 starts.
While these two teams have split 14 meetings this year, the Orioles have won six of eight at Tropicana Field.