Chelsea recorded a vital win against another of the title hopefuls, but it was a hard, defensive performance that ushered in the Jose Mourinho era at Stamford Bridge.
The Blues opened with a diamond formation in midfield, with Frank Lampard at the front, Claude Makelele anchoring and Alexei Smertin, making his debut alongside Geremi.
Didier Drogba, also made his Chelsea debut up front, with right back Paulo Ferreira and goalkeeper Petr Cech also starting for the first time.
Manchester United opened the encounter with more composure and had the first half-chance after just six minutes, when Liam Miller sent in a right-wing cross which was met on the edge of the box by John O'Shea, but his weak header ambled wide.
Three minutes later Ryan Giggs, wide on the left floated in an excellent ball, but Alan Smith could not direct his header on target.
Chelsea's first effort on the United goal after 13 minutes saw Drogba flick a Lampard free-kick wide.
Two minutes later Chelsea broke the deadlock. Quinton Fortune missed a clearance and the ball fell to Geremi, who ran 30 yards to send in a angled ball to Drogba. The Ivory Coast international cleverly headed the ball in to the path of Eidur Gudjohnsen, who lifted it over Tim Howard before slotting it home under pressure from Keane.
United almost hit back within a minute with a fine Paul Scholes piledriver of a free-kick which went inches wide of the right post.
The home side opened up United again after 18 minutes, but this time Howard reached the ball ahead of Drogba from a Lampard throughball and the chance was wasted.
On the half-hour mark good possession for United almost saw an equaliser. First a Alan cross to Giggs was smothered by Cech, before Scholes hit a snap-shot wide.
Five minutes later Lampard won the ball and touched it to Drogba, who was ruthlessly fouled by Roy Keane on the edge of the area. The resulting free-kick saw Lampard arrow a low drive past the wall, but also beyond Howard's right post.
The visitors started the second half in determined fashion and within a minute a Scholes left footer from the edge of the area was blocked by John Terry.
Smith's flicked header, from the edge of the area from a Gary Neville cross, went wide after 58 minutes and Chelsea quickly countered with Howard again alert to get to the ball before Gudjohnsen.
Mourinho substituted the tired Drogba on 70 minutes, replacing him with yet another new signing, Mateja Kezman.
The change prompted Sir Alex Ferguson to make a change of his own and Diego Forlan replaced Eric Djemba-Djemba shortly afterwards.
Within seconds he tried to weave his way through the Chelsea defence but Cech grabbed the ball before the striker could finish.
The Uruguayan had another chance moments later, but this time blasted his shot high and wide into row Z of the South Stand.
United should have levelled eight minutes before the final whistle when Smith put in an excellent right wing cross which Giggs met powerfully with his head, but could not direct on target.
Ferguson's last throw of the dice saw him bring on Kieran Richardson and David Bellion with six minutes remaining.
However, the move made no difference to the game and the Red Devils started their season with what could prove to be a costly defeat.