Delabar struck out a club-record four batters in a single inning, while Sierra hit the first home run of his major-league career in an extra-innings 3-2 win over the Chicago White Sox.
Delabar, who finished with six strikeouts in the 10th and 11th innings, said Monday he would make room in the trophy case for four balls after also becoming the only pitcher in history to strike out four batters in an extra inning. He managed the feat after White Sox catcher Tyler Flowers struck out but still advanced on a passed ball.
Delabar was so good manager John Farrell said the right hander would have pitched another inning if the game went on.
"I just felt good today. I had a couple days off. Kind of took it light the last couple days and everything was ready to go," said Delabar. "There's all kinds of records out there that guys can set and I'm just privileged to be part of it."
Delabar (3-1) replaced closer Casey Janssen, who allowed the tying run on Adam Dunn's second homer of the night in the ninth. Janssen settled down to finish the inning, and then sat in the dugout watching his teammate put on a show.
"It's impressive. That's tough to do. I mean, he was nails tonight," said Janssen.
Sierra meanwhile shook hands with reporters after the game and struggled to keep his composure. The 23-year-old Dominican Republic native, who made his major-league debut on July 31, gave Toronto (55-60) a 2-1 lead in the seventh after sending a 1-1 pitch from Chicago starter Jake Peavy over the centre-field wall.
"Very excited. I looked for a good pitch to help my team and I'm very excited. My first home run in the big leagues," said Sierra. "It's hard right now, it's hard because it's my first time here. I'm not very experienced and a little nervous."
Delabar and Sierra's performances were rewarded in the 11th when David Cooper singled in Kelly Johnson from third base to win the first of a four-game series against the White Sox.
Delabar's appearance overshadowed a solid night by Toronto starter Carlos Villanueva, who tied a season-high with eight strikeouts and was effective through seven innings of work by allowing just five hits and one walk.
His lone blemish was a 469-foot rocket by Dunn in the fourth, the longest so far of the season at Rogers Centre. Dunn's two homers on the night gave him the major-league lead at 33.
"Adam Dunn makes the ballpark look like a Little League field every time he steps on the plate, and that was the case again tonight," said Farrell.
White Sox starter Jake Peavy went eight innings, allowing both earned runs while striking out six and walking two. His night was ruined when reliever Leyson Septimo (0-2) walked Johnson and Nate Jones gave up the hit to Cooper that ended the game.
Chicago's loss ended up being tempered by Detroit's 9-3 loss to Minnesota, keeping the White Sox (62-52) ahead of the Tigers by two games atop the AL Central.
"Besides Adam, we didn't really get anything going, didn't look fluid or anything," said Chicago manager Robin Ventura. "We have to get something else going besides waiting for home runs."
The Blue Jays opened the scoring in the third when Peavy lost control. He hit both Anthony Gose and Johnson, then gave up a single to Encarnacion that drove in Gose. Chicago limited the damage by catching Johnson in a putout on the same play to end the inning.
The lead didn't last long. Dunn responded by mashing a solo shot off the centre-field window to tie the game at one. His homer just edged a 467-foot bomb by Encarnacion against Cleveland on July 14.
Gose showed off his speed by stealing second in the fifth, but had to walk back to first after Rajai Davis was called out for interfering with Flowers' throw to second. That prompted a visit to the mound by Farrell, but the long argument with home plate umpire Brian Knight amounted to nothing.
Gose stole second again on the next at-bat, but the effort was made moot when Johnson popped up to end the inning.
Notes: Attendance at Rogers Centre was 16,828. ... Star right-fielder Jose Bautista (wrist) resumed swinging off a tee, although there remains no timetable for his return. Bautista has been out of the Blue Jays' lineup since July 16. ... RHP Brendan Morrow (oblique strain, back spasms) will make two more starts in double-A New Hampshire before making a return to Toronto. ... Farrell said third baseman Brett Lawrie (oblique strain) will likely begin a minor-league assignment in single-A Dunedin by the end of the week. ... RHP Henderson Alvarez (7-9, 4.58 earned-run average) gets the start for Toronto on Tuesday. Chicago counters with left Jose Quintana (4-2, 2.78 ERA).