Upgrading the rotation has been an offseason priority for the Red Sox, who formally announced a one-year, $10 million agreement with right-hander Garrett Richards on Wednesday.

A 15-game winner for the Angels in 2015, Richards has spent his entire career to date on the West Coast, logging just 198 2/3 innings over the past five seasons due to injuries. He spent last year with the Padres, finishing 2-2 with a 4.03 ERA over 10 starts and four relief appearances.

“At this point in my career, winning is the main factor in the decision of where I want to play,” Richards said. “A historic franchise like the Red Sox having interest in me, it made me want to come play for them. I looked at it like a challenge, playing in that division, but also going to a team that I know is going to score runs and have a lot of fun. These guys always look like they’re having a blast.”

Richards underwent Tommy John surgery that cut his 2018 season short. He returned to make three starts for the Padres in ’19 and was healthy during the shortened ’20 season, holding right-handed hitters to a .189 batting average and .589 OPS. San Diego moved him to the bullpen from mid-September through the end of the year.

Richards said that he received positive reviews about Boston from infielder Mitch Moreland, a Padres teammate last season. To make room on the 40-man roster, Boston designated right-hander Joel Payamps for assignment.

“I put in a lot of time in rehab into getting back on the field and making sure that I can keep the same stuff I’ve always had,” Richards said. “I think that’s just a credit to my hard work and the people who have been around me to help me get to this point. It’s been a lot of hours, a lot of time and effort going into this to get me back on the field.”

In 187 career appearances, including 128 starts, Richards has compiled a 47-41 record with a 3.62 ERA. He projects as an important part of a rotation that will include Eduardo Rodriguez, Nathan Eovaldi, Nick Pivetta and Martín Pérez.

Earlier this offseason, the Sox landed another depth piece in righty Matt Andriese, who can start or relieve. Ace Chris Sale isn’t expected back until around midseason, as he recovers from Tommy John surgery.

“I think it’s solid, and when you get Chris Sale back, that’s a huge addition to any rotation,” Richards said. “It’s going to be a chance for us to go out and pitch. I know that we’re going to score runs; those are historic in Boston. I feel like every time I’ve ever played Boston, there hasn’t been any less than five runs scored.”

The 42nd overall pick by the Angels in the 2009 MLB Draft, the 32-year-old Richards enjoyed his best season in 2014, when he went 13-4 with a 2.61 ERA in 26 starts. His year ended early in a start at Fenway Park, when he injured his left knee while attempting to cover first base.

“It was a long time ago. It’s something I’ve put in the past,” Richards said. “It hasn’t really given me any issues since then.”

Richards has permitted only 0.75 home runs per nine innings over his career, the second-lowest mark in the Majors since 2011 (min. 500 innings). He averaged 95.1 mph with his fastball last season, throwing the pitch 46.3 percent of the time. He also utilizes a slider, sinker and curve, notching a 39.5 percent whiff rate with his slider.

“If I can get to a two-strike count without throwing somebody a slider, I think I’ll have a pretty high success rate,” Richards said. “I’m excited to get there with my teammates and start building relationships. I think a good rotation is one that enjoys being around each other and enjoys talking about the game, so I’m excited to start picking these brains.”