Detroit Tigers prospect Josh Lester hit an extra-innings grand slam that gave the West Michigan Whitecaps their seventh straight win Friday. (West Michigan Whitecaps photo)

The West Michigan Whitecaps beat the Dayton Dragons 7-5 in 12 innings Friday to win their 7th consecutive game and maintain their status as the team with professional baseball’s best record.

The Dragons, who started Friday tied for the second-best record in Minor League Baseball, rallied for three runs in the 7th and 8th innings to tie the score 3-3 and ultimately send the game into extra innings. Josh Lester’s grand slam in the top of the 12th inning won it for the Whitecaps, but not before the Dragons scored two more runs on a Bruce Yari homer in the bottom half.

Lester had three hits in the game, and teammate Jacob Robson had four.

The Whitecaps now have a 33-14 record. The only other team in professional baseball with 33 wins is the Houston Astros, who have 16 losses. West Michigan has a .702 winning percentage, better than Houston’s .673 mark.

The Triple-A Lehigh Valley IronPigs have Minor League Baseball’s second-best record, 32-15 (.681 winning percentage), just ahead of Dayton’s 31-16 record that gives the Dragons a .660 winning percentage.