CINCINNATI – Maybe the Mets should have spent a little more of that money on the bullpen.

Adam Dunn hit a tying, two-run homer in the ninth, and Joe Randa followed with a solo shot off Braden Looper that sent the Cincinnati Reds to a pulsating 7-6 victory yesterday in front of the largest crowd in Great American Ball Park history.

Dunn also had a three-run homer in the first inning off Pedro Martinez, the only ball hit hard in his six innings of domination. The former Boston ace struck out 12 during an electrifying debut.

But the Mets were left standing in place with heads down while Randa raised his fist triumphantly and rounded the bases, providing a last at-bat ending to his first game with the Reds, who struck out 16 times but pulled it out with four runs against the bullpen.

Until that moment, the Mets were feeling good about their off-season overhaul – one that skimped a bit on relievers. The expensive makeover started paying off immediately. Martinez allowed only three hits and Beltran hit one of the Mets’ three homers, building a 6-3 lead.

The Mets committed $172 million to those two players, giving the Yankees a run for their money when it came to making off-season headlines.

Martinez blew away the Reds and any doubt that at age 33 he can still dominate. After Dunn’s first homer, he struck out 12 of his last 14 batters.

He became the fourth pitcher to amass 100 double-digit strikeout games, joining Nolan Ryan (215), Randy Johnson (204), and Roger Clemens (108). The crowd of 42,794 thought it could get to Martinez by taunting him in the first inning. It should have known better than to dust of the “Who’s Your Daddy?” chant used by Yankees fans last year.

The cheer didn’t work. All it did was get him pitching like the old Pedro. The fans broke into the “daddy” chant while Martinez was in the process of fanning Randa to start his strikeout streak. With his fastball snarling in at 94 mph, Martinez didn’t allow a hit after the first inning and walked two before letting the bullpen take over in the seventh.

Manny Aybar gave up Jason LaRue’s RBI double in the seventh. Looper then let it slip away in only 14 pitches – Austin Kearns’s single, Dunn’s homer, and Randa’s final swing.

Beltran hit a two-run homer in the third off Paul Wilson, a former Mets no. 1 draft pick making his first opening day start at age 32. Beltran also singled home the tiebreaking run in the seventh off David Weathers.

Beltran, Jose Reyes, and Cliff Floyd had three hits apiece for the Mets. Kaz Matsui homered in his first at-bat – the second straight year he’s done that – and Floyd hit a two-run homer off Kent Mercker in the seventh to make it 6-3.