The San Francisco Giants' South Korean rookie Lee Jung-hoo blasted his first career big league home run in just his third game.

Lee went deep off Tom Cosgrove of the San Diego Padres in the top of the eighth inning at Petco Park in San Diego on Saturday.

With the count at 1-1, Lee, who bats left-handed, drilled a sweeper from the lefty reliever and sent it 406 feet into the right field seats. The ball left Lee's bat at 104.4 miles per hour.

Lee's homer kick-started a six-run inning for the Giants. After Lee made it 4-1 for the Giants, Wilmer Flores had an RBI single, and Michael Conforto smacked a grand slam to blow the game wide open at 9-1.

Lee, after a seven-year run in the Korea Baseball Organization, signed a six-year, US$113 million contract with the Giants after getting posted in December. It was the largest contract awarded to a KBO player in posting.

Lee batted a solid .343 in 13 spring training games and then hit the ground running to start his first regular season.

Lee collected his first MLB hit and RBI in his very first game on Thursday, and went 2-for-5 with another RBI the next day.

In Saturday's game, Lee had another "first" out of the way with the solo shot in the eighth inning. (Yonhap)