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6/27/2014 9:54 A.M. ET

Mariners top pick Jackson impresses in pro debut

Sixth overall selection racks up two hits, runs, RBIs in first Arizona League game

Alex Jackson, the sixth overall pick in the 2014 First-Year Player Draft, was impressive in his professional debut on Thursday, as the 18-year-old collected two hits and a walk in the rookie-level Mariners' 10-8 defeat of the Padres in the Arizona League.

Serving as the team's designated hitter, Jackson went 2-for-4 with a triple, a run, a walk and two RBIs. He was primarily a catcher in high school but is expected to transition to the outfield in the Minor Leagues.

In Jackson's first professional at-bat, he singled up the middle. He came around to score on an RBI single by the Mariners' 2014 second-round pick Gareth Morgan, who finished 1-for-3 with two walks and three RBIs in his pro debut. Jackson struck out in his next two plate appearances -- once swinging and once looking -- before walking and scoring in the seventh inning. He rounded out his night with an RBI triple in the eighth.

Jackson officially signed with the Mariners on Monday for a reported $4.2 million. He made his professional debut three weeks to the night after he was drafted.

Teddy Cahill is a reporter for MLB.com. Follow him on Twitter at @tedcahill. This story was not subject to the approval of Major League Baseball or its clubs.