Hernandez came up with the bases loaded and grounded a single into left field. Pinch runner Santiago Espinal scored easily and Randal Grichuk slid in safely just ahead of the throw by left fielder Mason Williams.
Cole Sulser (1-4), who surrendered a game-ending homer to Grichuk on Friday, issued three walks and Hernandez’s hit to take the loss.
Jose Iglesias delivered a go-ahead RBI single on a dribbling infield single in the top of the ninth inning against Toronto reliever Anthony Bass (2-1).
Ryan Mountcastle hit his first two big league homers for Baltimore, which lost its fifth straight. Mountcastle had three hits to run his average to .393 (11 of 28) since making his major league debut on Aug. 21.
Toronto earned its fourth straight win. Vladimir Guerrero Jr. extended his career-best hitting streak to 12 games, and Hernandez had two hits to extend his hit streak to 11 games, also a career high. Cavan Biggio extended his on-base streak to 22 games with an RBI single in the fifth inning.
Mountcastle led off the second with a towering drive to left. He hit a two-run shot in the sixth to give Baltimore a 4-3 lead. Both homers came off Toronto starter Tanner Roark.
Iglesias, Renato Nunez and Pedro Severino each had two hits for the Orioles, who are now 0-6 against Toronto this season.
Toronto tied it at 4 with two out in the eighth, getting a Hernandez single and Guerrero walk before Rowdy Tellez came through with an RBI single.
The Orioles completed two trades, dealing right-hander Tommy Milone to Atlanta for two players to be named and sending right-hander Mychal Givens to Colorado for infielders Terrin Vavra and Tyler Nevin and a player to be named or cash considerations.
Milone went 1-4 with a 3.99 ERA over six starts in his first season with the Orioles. Givens, 30, spent parts of six seasons with Baltimore.
Vavra, 23, was a third-round pick by the Rockies in the 2018 draft. Nevin is the son of former big league slugger Phil Nevin.
Right-hander Hunter Harvey and lefty Keegan Akin took over Baltimore’s vacant roster spots. The trade deadline for the pandemic-shortened season is Monday.
“Young clubs get even younger at the deadline,” Orioles manager Brandon Hyde said. “We’re young already and we’re going to stay inexperienced for this last month, and we’ll do the best we can with the guys we have.”
Orioles: Harvey (forearm strain) was activated from the IL, leaving three players on the 10-day injury list: RHP Shawn Armstrong (left SI joint inflammation), INF Chris Davis (left knee patellar tendinitis), and OF Austin Hays (non-displaced rib fracture).
Blue Jays: SS Bo Bichette (sprained knee) took ground balls, ran sprints, and hit in the cage. … Closer Ken Giles (forearm strain) felt good after a bullpen session, and manager Charlie Montoyo envisions “at least two more live batting practices before he comes back.” Montoyo added: “If he looks like he did before, there’s no reason why he wouldn’t be our closer again.” … RHP Nate Pearson (elbow tightness) and RHP Matt Shoemaker (shoulder inflammation) played catch from 90 and 60 feet, respectively.
Orioles: With the trade of Milone, originally scheduled to face the Blue Jays on Monday, Hyde did not indicate who would be getting the start. “It’s still up in the air,” he said. “We’re going to take a long look and figure it out.”
Blue Jays: RHP Chase Anderson (0-0, 3.68 ERA) will start in Monday’s finale of the four-game series against Baltimore.