The game will be at 4 p.m. PT on Sunday, July 10, at Petco Park as part of Major League Baseball's All-Star week festivities.
O'Neill, a native of Canada, and Unsworth, who hails from South Africa, were among the 25 players who were named to the World Team. Another 25 of baseball's premier prospects were selected to the U.S. squad
O'Neill, ranked by MLBPipeline.com as the Mariners' No. 4 prospect, is having a big season for Jackson producing a slash line of .310/.371/.532 with 13 homers and 59 RBIs in 73 games. The 21-year-old from Maplewood, B.C., was a third-round pick of the Mariners in the 2013 Draft and hit .260 with 32 homers and 87 RBIs for Class A Advanced Bakersfield in 2015.
Unsworth, 23, has also been outstanding for Jackson, going 3-1 with a 1.16 ERA in nine starts, with 35 strikeouts and seven walks in 46 2/3 innings. The native of Durham, South Africa, signed with the Mariners as a non-drafted free agent in 2009.
Unsworth threw eight shutout innings with just two hits allowed for South Africa in a victory over New Zealand in a World Baseball Classic Qualifier tournament in February. He currently is on the seven-day disabled list with Jackson due to a hamstring injury and will not be able to play in the Futures Game, however.