LONDON, England (AP) — Demba Ba’s debut double helped Chelsea make a perfect start to their FA Cup defence with a 5-1 rout of Southampton in the third round, while Robin van Persie scored an injury-time equaliser to salvage a 2-2 draw for Manchester United at West Ham and earn a replay.

A day after completing his move from Newcastle, Ba took just 35 minutes to score at Southampton to cancel out Jay Rodriguez’s goal.

After further Chelsea goals from Victor Moses and Branislav Ivanovic, Ba netted his second before Frank Lampard wrapped up the rout from the penalty spot.

Newcastle struggled without Ba, however, and were the only Premier League side to be ousted by lower-league opposition as Alan Pardew’s side lost 2-0 at second-tier club Brighton.

At West Ham, Joe Cole had a successful return as he set up two nearly identical goals for James Collins as the Hammers looked to knock off United, but Van Persie came on as a substitute to rescue the draw with a clinical finish in stoppage time.

Manchester City had no trouble ousting League Championship club Watford, with a 3-0 victory, while Tottenham beat third-tier club Coventry by the same score in a rematch of the 1987 final.

The biggest upsets were provided by fifth-tier nonleague sides overcoming second-tier opposition as Macclesfield beat League Championship leader Cardiff, 2-1, and Luton defeated Wolverhampton Wanderers, 1-0.

At Southampton, the 27-year-old Ba showed just how valuable he can be for Chelsea’s quest for silverware this season as Fernando Torres was rested on the bench.

Ba’s 14th goal of the season — and first for Chelsea — came after Juan Mata initially attempted to score from an acute angle, cancelling out Rodriguez’s opener.

Chelsea went in front on the stroke of half-time after Moses collected a cutback from Ashley Cole and struck into the net. Seven minutes into the second half, Ivanovic headed in Mata’s cross, and Ba found the target again in the 61st after being setup by Eden Hazard.

The late penalty from Lampard — after Steven Davis handled — allowed the 34-year-old midfielder to move to joint second on Chelsea’s all-time leading scorers list alongside Kerry Dixon.

As Southampton went out of the cup, it was a successful day for another south-coast side as Brighton eliminated Newcastle for the second successive season.

Andrea Orlandi put Brighton ahead in the 33rd, hooking the ball into the net with the outside of his boot after meeting Wayne Bridge’s cross.

Three Premier League clubs face replays after being held by lower-league opposition. Wigan drew 1-1 with Bournemouth, Fulham were held by the same score by Blackpool, and Sunderland drew 2-2 with Bolton.