The 23-year-old Contreras -- ranked as the Reds' No. 5 prospect on MLB.com -- appeared in nine games for the Blue Wahoos this season, including three starts. He went 2-1 with a 2.70 ERA and held opponents to a .195 batting average against. He features a fastball that can reach the upper-90s and a good changeup.
"I feel very excited; first game as a big leaguer, it was awesome," Contreras said. "I was a little nervous with it being my first game. It's tough if you don't get nervous. But it was very, very good. I was making quality pitches."
Manager Bryan Price was happy for Contreras, who is the second relief pitcher to make his big league debut in as many days for Cincinnati. Right-hander Jumbo Diaz made his first appearance in the seventh inning on Friday.
"Carlos was terrific," Price said. "I don't know what that experience is like as a player, unfortunately, to come into that situation. It was an 11-1 game. However, it was a Major League debut in front of a sold-out capacity crowd against a team that scored 14 the night before, in the middle of their lineup. I thought he handled it really well."
Bernadina, who hit .153 (9-for-59) with three doubles and five RBIs, was previously designated for assignment on May 3 when Skip Schumaker was activated from the disabled list, but returned to the club three days later when Jay Bruce went on the DL.
Reds relievers haven't been able to catch their collective breath as of late. In Friday's series opener against the Blue Jays, Cincinnati used six relievers who combined to give up nine runs, including three homers. It marked the first time Reds relievers have surrendered nine runs in a game since giving up nine over four innings on June 9, 2013 against the Cardinals.
Friday's collapse came on the heels of an extra-inning loss, 4-3, on Thursday against the Brewers in Milwaukee. The Reds also used six relievers in that game, five of whom pitched again on Friday (Sam LeCure, Logan Ondrusek, Manny Parra, Jonathan Broxton and Aroldis Chapman).
"A day off for the bullpen would be a huge step in the right direction," Price said. "When I talk about a quality start, I'm not talking about six innings. I'm talking about seven or eight innings. A couple of those back-to-back would do us a service for sure. We're going to need the starters to pitch, and if they don't pitch efficiently, they're going to still have to stay out there. That's just the way it is right now."
Saturday's starter for Cincinnati, Mike Leake, answered the call, giving the Reds eight strong innings to give the bullpen a breather before Contreras came into the game.