CINCINNATI – The last time the Mets started this badly, Casey Stengel was calling the shots.

Aaron Harang allowed only one single in 6 1/3 innings yesterday, and D’Angelo Jimenez had a pinch two-run double off Kazuhisa Ishii that sent the Cincinnati Reds to a 6-1 victory and three-game sweep of the Mets.

With a combined four-hitter, the Reds improved to 3-0 for the first time since 1990, when they won their first nine and swept Oakland in the World Series.

The Mets, meanwhile, haven’t lost their first three games since 1964, Stengel’s third year managing a fledgling club that redefined losing. The Mets dropped their first nine games in the inaugural 1962 season, on their way to a standard-setting 120 losses. They went 0-8 and lost 111 a year later. By those standards, their 0-4 start in 1964 was deemed an improvement.

This slow start under first-year manager Willie Randolph is nothing but trouble.

The Mets grabbed off-season headlines with their high-priced overhaul, committing $172 million to Pedro Martinez and Carlos Beltran. Their $105 million payroll is the NL’s largest and ranks third overall, trailing only the Yankees and Red Sox.

The bullpen blew a ninth-inning lead in the season opener, won by Joe Randa’s homer. Randa had a grand slam and six RBI as Cincinnati won the second game as well.

Harang completed the sweep with one of the best performances of his career, allowing only three walks and Ramon Castro’s second-inning single before letting the bullpen take over.

The Mets failed to get an extra-base hit. David Wright and Marlon Anderson had eighth-inning singles off Joe Valentine, and Jason LaRue’s passed ball let in their only run. New York loaded the bases with two outs in the ninth on a single and two walks off David Weathers, but Danny Graves retired pinch-hitter Mike Piazza to get his first save.

Harang topped Kazuhisa Ishii, who allowed only two costly hits over 6 2/3 innings. Wily Mo Pena hit a solo homer in the second, and Jimenez’s double sparked a three-run rally in the seventh.

Ishii came to the Mets in a March 20 trade with the Dodgers, hoping to shake his habit of working deep into counts and walking a lot of batters. He walked Ryan Freel and Felipe Lopez to open the Reds’ first, setting himself up for familiar trouble.

Kaz Matsui let Sean Casey’s potential double-play grounder get through him for an error that let in a run, and Austin Kearns followed with a sacrifice fly.

Pena led off the second inning with a homer, the last hit that Ishii allowed until the seventh. The left-hander got into a flow after the homer, retiring the next 11 batters and fanning five straight during that stretch.

Freel got a warm reception from the fans during pregame introductions. Freel, playing for the first time since his drunken driving arrest on Monday night, had an RBI single and two of the four walks off Ishii.