"I think it's the right decision because I'm not doing my job," said Cordero, who surrendered a walk-off grand slam to Brandon Inge in Tuesday night's 7-3 loss to Oakland.
"We're trying to win. The Blue Jays did a great job putting this team together, trying to win the [American League East] division and go to the playoffs. If I keep doing what I've been doing, we're not going anywhere."
Cordero took over as closer on April 21 when Santos was placed on the 15-day disabled list with inflammation in his right shoulder. Cordero, who is second on the all-time list among active pitchers with 329 saves, converted his first two opportunities before things took a turn for the worse.
The 36-year-old has allowed at least one run in each of his past four outings. On the season, he has surrendered 12 runs in just 11 1/3 innings while posting a 2.29 walks/hits per inning pitched ratio.
Cordero has experienced trouble locating his fastball down in the zone, and his slider doesn't have the late-breaking action that it normally does. That has led to four home runs allowed and the prolonged struggles on the mound that forced manager John Farrell's hand.
"With the changing role, get him back to the middle of the game when those opportunities present themselves to get some work in less leveraged situations," said Farrell, who added that Jason Frasor, Darren Oliver and Luis Perez will serve in the primary setup roles.
"A lot of this is still confidence and the mental side of it. We want to build positive outings to get him some momentum, so when those opportunities later in the game arise, he's had some positive reinforcement to go into that."
The Blue Jays will now turn to Janssen in an effort to solidify the ninth inning. Toronto, which tied for the American League in blown saves last season with 25, is just 4-for-11 in similar opportunities this year, and it's clear that better results are needed in order to make a run in the competitive AL East.
Janssen was sympathetic to Cordero's situation, but also is looking forward to his new role -- even if it's just until Santos returns at the end of May or in early June.
"It's definitely bittersweet," said Janssen, who has a 5.23 ERA in 10 1/3 innings this season. "You never want to see a teammate struggle. I can't say enough about what [Cordero] has done and the kind of person he is. Hopefully I can get some outs and get us some wins.
"I'm excited that [Farrell] believes in me, and I'm ready to help in any way possible. My first month wasn't what I hoped, but I'm feeling a lot better and I'm ready to take on this challenge."