Theo Walcott was pleased Arsenal avoided the same fate as some of their Premier League counterparts as the FA Cup holders held off a spirited Brighton fightback to progress to the fifth round yesterday

Manchester City, Chelsea, Tottenham and Southampton all suffered shock defeats on Saturday but Arsenal managed to avoid the same fate with a 3-2 victory at the Amex Stadium.

Arsenal were seemingly cruising when Walcott gave them the lead inside 90 seconds and Mesut Ozil doubled their advantage in the 24th minute.

Chris O'Grady pulled a goal back for Brighton five minutes into the second half, but again Arsenal seemed home and hosed when Thomas Rosicky restored their two-goal advantage four minutes later.

Brighton then set up a nervy final 15 minutes for Arsenal when Sam Baldock scored but the Gunners held on to take a step closer to retaining the trophy they won by beating Hull at Wembley last May.

Walcott missed the extra-time triumph against the Tigers through injury but was instrumental in Sunday's victory over Chris Hughton's side, and the England forward was relieved that Arsenal did not follow some of their league rivals out of the competition.

"It's nice to get three goals but we will be disappointed with the goals we have conceded," he told BT Sport 1.

"We will look back at that and think what we could have done better but in the FA Cup it doesn't matter how you perform, as long as you get through it's the main thing."

Walcott added: "I think in patches it (Arsenal's performance) was very good. I think the (Brighton) goals put us under pressure.

"Rosicky got the third one which eased it but you've got to give credit to Brighton. They came at us and yesterday, with all the results not going for the Premier League teams, it was always going to be a tough game. That's what the FA Cup is about."

Arsene Wenger will become the most successful manager in FA Cup history if the Gunners retain the trophy at the end of the season but he is not looking too far ahead.

"We have a goal (to win the trophy), of course, but it's such a long way to go and you've seen today again the tie is not predictable until the last minute," the Frenchman said.

"You have to fight for it, we are ready for a fight."

Hughton, who succeeded Sami Hyypia as Brighton boss on New Year's Eve, was pleased with his players' response after going two goals behind but not with their start to the game.

"I'm delighted with the way we finished, but I'm not happy with the first-half performance because I felt an Arsenal team coming here - as good as they are - we were second best certainly for the first half an hour," he said.

"I'm really delighted with what we showed at the end. I think at the end of the game what you want is a home crowd to see a Brighton team that has had a real go and I think they've seen that."

Meanwhile, Paul Lambert insisted Fabian Delph is irreplaceable at Aston Villa after the England star penned a new deal.

The midfielder has signed a four-and-a-half year contract, which was announced just before Villa's 2-1 FA Cup win over Bournemouth on Sunday.

Delph, who missed the game with an Achilles injury, was due to be out of contract at the end of the season and had been linked with Liverpool.

A breakthrough in talks was made earlier this month and Lambert admitted the 25-year-old would have been a huge loss.

"If you lose someone of that ilk it's going to cost you a fortune to replace him," he said. "It would take millions to replace him and we obviously can't do it.

"I don't know what his value is, £15million? Whatever it is we're not in a position to go and do things like that at this minute in time.

"It's great for the club he is definitely staying, it makes common sense.

"It's great for him as it puts everything to bed. I know from my own experience when you're coming out of contract your head's all over the place at times. He will be settled and he'll be a big driving force behind this club in the next few years."

And Lambert insisted Villa would not sell Delph should other clubs come in for him later.

"There's no way that's going to happen. With the way he handles himself, no way that's going to happen," he said.

Ron Vlaar's future remains uncertain with his contract ticking down, but Lambert will continue to talk to his skipper.

He added: "He holds the ace card, as any player does when they are out of contract, but if we can keep talking let's see. Everyone assumes Ron and Fabian were going to go, we've got Fabian and we just need to keep it going now."

Carles Gil's opener against Bournemouth - on his full debut - was just Villa's second goal in 663 minutes and Andreas Weimann made it 2-1 with 19 minutes left before Callum Wilson's stoppage-time consolation.