UPDATE 4-Soccer-Blunder helps Napoli hand Inter first defeat

(adds Mancini quote)

By Paul Virgo

ROME, March 2 (Reuters) - Marcelo Zalayeta capitalised on an early blunder by Inter Milan keeper Julio César as Napoli ended the leaders's unbeaten record in Serie A on Sunday with a 1-0 home win.

Zalayeta chipped into an empty net in the third minute after Cesar, who saved a penalty from the Uruguayan striker in the second half, tapped an intercepted long pass to him instead of hoofing away.

Inter still have a six-point lead over AS Roma, who are on 55 points from 26 games after thrashing Parma 4-0 on Saturday.

Earlier on Sunday Fiorentina beat third-placed Juventus 3-2 to move within a point of the Turin side in the standings.

Fifth-placed AC Milan are four points adrift of the Florence club and the Champions League qualification zone after being held 1-1 by Lazio at the San Siro on Saturday.

Napoli continued to dominate after going ahead and César repelled efforts by Marek Hamsik and Paolo Cannavaro before saving Marco Materazzi's blushes before halftime when he palmed the defender's mishit attempted clearance off the line.

The Brazilian keeper was busy again in the second half, pushing away a well-struck Hamsik shot and saving the 75th minute spot-kick, conceded for a foul he had committed on Walter Gargano.