When the Red Sox remade their rotation over the winter, Wade Miley was the acquisition fans knew the least about.
Justin Masterson was a well-regarded former Sox prospect and Rick Porcello a familiar opponent with the Detroit Tigers. Both had appeared in playoff games, too.
Miley, a mid-rotation starter with the Arizona Diamondbacks, was anonymous by comparison despite having made the National League All-Star team in 2012. He had never faced the Sox and had only five starts against other American League East teams.
In-person scouting and detailed statistical analysis prompted the Red Sox to trade for Miley in December. On Thursday, the Sox demonstrated more faith by signing the 28-year-old lefthander to a three-year deal worth at least $19.25 million with an option for a fourth season.
For Miley, who made $523,500 last season, the new contract brings security. There was a $500,000 signing bonus with a $3.5 million base salary for the coming season. His salary then escalates to $6 million and $8.75 million.
The Red Sox hold a $12 million option for 2018 or can give Miley a $500,000 buyout.
Miley also could earn $2 million in incentives. In all, he could make as much as $32.75 million over four seasons.
“I’m just excited to get the commitment. Hopefully everything works out and we can win some ballgames,” Miley said during a conference call. “I’m just thrilled to be a part of Red Sox Nation and part of the organization.”
For the Red Sox, the deal provides cost certainty for at least three seasons with a pitcher they project to be in their rotation. With Masterson and Porcello signed to one-year contracts and Clay Buchholz in the final guaranteed year of his deal, tying up Miley for at least three years made sense.
Miley is 34-33 with a 3.74 ERA over the last three seasons, and averaged just shy of 200 innings. He leads the big leagues in starts by a lefthander (66) over the last two years.
“We like him and we believe he’s going to help us win games. When we traded for him our full expectation was he could be here for a while,” general manager Ben Cherington said.
The sides could have agreed on a one-year deal. But Miley was interested in a multiyear contract.
“You’re trying to find a sweet spot where it feels fair to the team and feels fair to Wade, and we were able to do that,” Cherington said. “We’re looking forward to Wade being part of the rotation.”
The Red Sox traded three players — righthanders Rubby De La Rosa and Allen Webster and minor league infielder Raymel Flores — to Arizona on Dec. 12 to obtain Miley.
The deal avoided an arbitration hearing that had been scheduled for this month. Miley was seeking $4.3 million, the Red Sox offering $3.4 million.
The Sox have not gone to an arbitration hearing with a player since Rolando Arrojo in 2002.
With Miley signed and the recent addition of relievers Alexi Ogando and Robbie Ross, Cherington does not expect any major transactions before spring training starts Feb. 20.
“I would expect the group we have for spring training is in place. I’d be surprised if there were any additions,” Cherington said.
Alex Speier of the Globe staff contributed to this report.