The 35-year-old left-hander has not appeared in a major-league game since 2012 due to a shoulder injury. But the Jays scouted him over the winter and liked what they saw.
"If we can get him on the mound and be healthy, we don't have any doubts he's can be a very good starter," Blue Jays general manager Alex Anthopoulos told reporters Friday. "His stuff was still good during the winter, the change-up's still there. He's a great competitor, a great athlete.
"Again it's a minor-league deal so we really don't have anything to lose. Just a complete upside."
If he does make the team, the Venezuelan will make a pro-rated contract of US$2.5 million with bonuses. If he doesn't, the two will likely part ways.
"A guy like Johan, he's not coming here to go pitch in the minor leagues. He's coming here to get ready, get right and see if he can help us win games in Toronto," said Anthopoulos. "It's a bit of a unique one."
Santana is expected in camp this weekend.
The GM said it's "highly unlikely" Santana would be ready for Opening Day, given he has just started his throwing program.
"We're going to bring him in, he'll go at his own pace and we'll see what he has and how he looks," said Anthopoulos, who called it a "no-risk deal."
Santana's career record is 139-78 with an earned-run average of 3.20 over 360 games (284 starts) in 12 seasons with the Minnesota Twins and New York Mets. He won the AL Cy Young Award in 2004 and 2006.
Anthopoulos said his signing did not mean Aaron Sanchez was headed to the bullpen as closer rather than the starting rotation.
"There's no connection whatsoever," he said.
Anthopoulos added that Santana was interested in joining the Jays and would help younger pitchers.
"We're very excited to have him ... clearly he's a very competitive guy and believes in himself. We certainly believe that there's a lot left. It's just a question of getting him right, getting him strong."
Santana, who went 6-9 with the Mets in 2012 with a 4.85 ERA, will wear No. 57 for the Jays. He has earned some $156 million over his career, according to baseball-reference.com.
Follow @NeilMDavidson on Twitter.Suggest a correction