The Astros prospect went 5-for-5 with two homers, a double and a career-high six RBIs as the Legends fell, 10-9, in 10 innings in the first game of a five-game set at West Virginia's Appalachian Power Park.
The Astros' 20th-round pick in the 2009 Draft hit a pair of homers for the Tri-City ValleyCats last July 17, but had never before driven in more than four runs in a game. He collected five hits earlier this season at Greenville on April 27.
The 22-year-old leads the South Atlantic League with a .355 batting average, .422 on-base percentage and .572 slugging percentage. His 60 RBIs are second only to teammate Kody Hinze's 65.
He entered Thursday's contest, however, just 3-for-20 in his last six games.
The Legends jumped out to an early lead in the first inning when Martinez doubled home leadoff man Miguel Arrendell and later scored on a double by Jacob Goebbert. Lexington tacked on four more runs in the second, capped by Martinez's two-run shot to left.
Martinez's two-RBI single in the fourth pushed Lexington's lead to 8-1, and after West Virginia put four runs across in the sixth, he led off the seventh with his second homer of the game and 12th of the season. He collected his fifth hit with a leadoff single in the ninth.
Things began to unravel for the Legends in the eighth inning when West Virginia scored three times to draw within a run, 9-8. The Power tied the game with back-to-back doubles by Ramon Cabrera and Kyle Morgan in the ninth, then won it on Jesus Brito's sacrifice fly in the 10th.
It was Lexington's fourth loss in 41 games in which it led after eight innings.
Michael Schurz (0-2) took the loss for the Legends, allowing two runs -- one earned -- on two hits and two walks in 1 1/3 innings. He struck out two, hit a batter and committed a throwing error.
West Virginia reliever Zachary Foster improved to 4-2 after giving up two hits in one scoreless frame.
Catcher Ramon Cabrera led the Power offense, going 3-for-3 with two doubles, two RBIs and two runs scored.