South Korean slugger Lee Dae-ho has made the Seattle Mariners' 25-man roster, an informed baseball source told Yonhap News Agency Monday, a move that gives the 33-year-old his first big league job.

The Mariners have yet to unveil their Opening Day roster. On Sunday local time, the M's said Lee had made their 40-man roster and was likely to be added to the team's 25-man roster in the coming days.

According to the source, the Mariners have already informed Lee that he'd be on the 25-man roster. Lee stands to make $1 million and could make as much as $4 million with incentives.

An official with Lee's Korean agency, Montis Sports Management Group, also said Seattle has told Lee that he'll be on the 25-man roster.

"Thanks to the support of the fans, I've realized my first goal," Lee said through the agency. "But I won't stop here. I will keep doing my best to put up even better numbers in the regular season."

The Mariners had to make a decision on Lee by Sunday. If he had failed to make the team, Lee could have opted out of his contract and become a free agent.

The first baseman/designated hitter signed a minor league deal with the Mariners in February with an invitation to spring training. He'd been battling for the right-handed backup first base job with Jesus Montero and Stefan Romero, behind left-handed hitting Adam Lind.

Lee went 1-for-4 later Sunday and is batting .250 for the spring with a home run and four RBIs in 18 games. The hulking veteran, listed as 6-foot-4 and 250 pounds, has also played solid defense at first.

"Dae-ho has the history of hitting left-handers and I think he's given us reason to believe in spring training," Mariners' general manager Jerry Dipoto was quoted as saying on MLB.com. "He's very prepared, very calm in the batter's box and I think he's gotten better every step of the way as we've gone along. It's been a pleasant surprise -- the defense and particularly the baserunning. He runs the bases really smart. His defense has been much better than we anticipated at first base."

Montero left camp Saturday and his locker was cleared out. The Mariners said they will make an official announcement on Montero on Monday, local time. Once among the game's top prospects, Montero is out of minor league options and had to clear the waivers first before he can be sent down to the minors. It's likely that the M's have already designated him for assignment and are waiting for the 48-hour waivers period to see if another club claims him.

Montero didn't play Sunday. He'd been batting .237 in the spring with no home runs and four RBIs in 38 at-bats.

Romero has put up the best offensive numbers of the three, with a .375/.390/.500 line, one home run and eight RBIs. 

Lee is a former Korea Baseball Organization regular season MVP who played his last four seasons in Japan's Nippon Professional Baseball. He enjoyed his most productive NPB season in 2015 with the Central League's Fukuoka SoftBank Hawks, with 31 home runs and 98 RBIs, both career-highs, in 141 games.

He was later voted the MVP of the Japan Series thanks to two home runs, eight RBIs and a .500 batting average in five games.

Lee is one of seven South Koreans in preseason action, along with Choo Shin-soo of the Texas Rangers, Park Byung-ho of the Minnesota Twins, Kim Hyun-soo of the Baltimore Orioles, Choi Ji-man of the Los Angeles Angels, Oh Seung-hwan of the St. Louis Cardinals and Lee Hak-ju of the San Francisco Giants.

Lee Hak-ju was reassigned to the Giants' minor league camp last week. Kim, an All-Star outfielder in the KBO, has been struggling at the plate -- .182 in 16 games -- and appears to be on a bubble. A Fox Sports report on Saturday said the Orioles have had internal discussions about possibly releasing Kim from his two-year, $7 million contract and letting him return to South Korea.

Two other South Koreans, Ryu Hyun-jin of the Los Angeles Dodgers and Kang Jung-ho of the Pittsburgh Pirates, are recovering from injuries and are expected to return to action after the start of the regular season. (Yonhap)