Tennessee (6-6) led 5-1 before the Flames rallied for four runs on four hits in the eighth to tie things up.
An infield throwing error in the top of the ninth inning made it possible for Illinois-Chicago (3-4) leadoff man Chad Schroeder to score the winning run from third base.
Tennessee freshman Nick Hernandez (0-1) was tagged with the loss after entering a tie game at the start of the ninth.
Tony Delmonico finished 2-for-4 with a home run for the Vols, while Ryan Jones had two RBIs.
ROCK HILL, S.C. - Junior Anthony Russell drove in both East Tennessee State runs, while four pitchers combined for a Bucs shutout in the Coca-Cola Classic at Winthrop Ballpark.
Junior Brandon Langston (2-1) scattered five hits and struck out three batters in 7 1-3 innings and allowed only three runners into scoring position.
After 3Â½ scoreless innings, Russell doubled to drive in C.J. Lee and give the Bucs (8-3) a 1-0 lead.
Russell added an insurance run with his third homer of the season in the sixth inning.
Sophomore Darren Caldwel came on to record the second out in the eighth inning, and senior Caleb Glafenhein retired the final four batters for his third save.
CHATTANOOGA - Monica Abbott notched her 151st win to tie an NCAA record in the opener, and Megan Rhondes fanned 19 in a perfect game in the nightcap.
Abbott struck out 18 in the top-ranked Lady Vols' 2-0 victory in the first game of a doubleheader at the Frost Classic in Chattanooga.
In the opener, UT senior left fielder India Chiles led the attack, going 3-for-3 with a run scored.
In the second game against Oakland, Tennessee racked up 15 hits, with Alexia Clay tallying her first career grand slam in the third inning. Tiffany Huff and Tonya Callahan each were 3-of-4 at the plate, while Lindsay Schutzler posted two hits.