Red Sox prospect Triston Casas let out two primal screams on Saturday during Team USA’s game versus Korea. The first came after he jump-started the Americans’ offense. The second came as he ended matters with a nifty pick of a bouncing throw at first base.

Home runs by Casas and A’s prospect Nick Allen highlighted a 4-2 triumph, which clinched Group B. With the win, the USA (2-0) will face the winner of Group A, Japan, on Monday. Whoever prevails there will advance to the semifinals, one win shy of the gold medal game, while the loser will head into an elimination game.

Team USA was kept quiet through the first three innings, as Korea starting pitcher Young-pyo Ko was nearly perfect. But in the fourth, Casas' two-run shot to right put Team USA ahead, 2-1. Allen followed with a solo blast to left field in the fifth before Tyler Austin added an RBI single.

The quick outburst supported the USA’s five pitchers, who struck out 14. Former Texas Rangers pitcher Nick Martinez got the start and dominated after allowing a run in the first inning. Beyond an RBI groundout by Hyun-soo Kim, Martinez struck out six of the next nine batters he faced and didn’t allow a runner past first. His day ended after five innings, as he allowed four hits and no walks with nine K’s.

Scott McGough, Edwin Jackson and Anthony Gose all posted zeroes to get the game to the ninth for David Robertson, a former closer for the Yankees and White Sox. He got into trouble immediately by issuing a leadoff walk before a double by KBO star Eui-ji Yang brought the tying run to the plate. But Robertson escaped the jam harmlessly enough with a sacrifice fly, a strikeout and fabulous defensive efforts by a couple of Boston Minor Leaguers, Jack López and Casas.