BRENTFORD manager Martin Allen believes that his side's best chance to pull off a giant-killing against Saints has gone.

The League One play off hopefuls have home advantage tonight and showed how tough they are to beat at Griffin Park when they scored two late goals to draw 3-3 with Sheffield Wednesday on Saturday.

But Allen reckons it will be even harder for the Bees tonight - despite the backing of a partisan home support. He said: "History shows that the underdog gets only one bite at the cherry so we know that Tonight's game will be even tougher than the one at St Mary's, without a shadow of a doubt.

"Our big opportunity was in the first game, this will be harder because they know about us now."

Allen believes that the gap between Saints and Brentford is so big that the visitors would be favourites to go through tonight - even if Harry Redknapp played his reserve side.

He added: "I've seen Southampton reserves a few times this season and there are six or seven of that side that would get into my first team.

"I've even tried to get one or two of them on loan. It didn't come to anything, unfortunately, but it just shows what we're up against. There'll be another terrific atmosphere. Both sets of supporters were superb at St Mary's.

"The Saints fans gave me stick last time but I'm used to that, I've had it throughout my career and before the kick off I took a step back and did my best to detach myself so I could savour the moment.

"I looked, listened and tried to take in everything that was going on so I could remember it all in years to come."

Holders Manchester United at home await tonight's winners in the last eight.

Allen added: "It's amazing that we're playing for a place in the quarter-finals against one of the biggest clubs in the world. Just over a year ago I was managing Barnet in an FA Cup qualifying tie at Bracknell, when four of my team were still playing non-league football!

" It's been a very steep climb since then and at times I still have to pinch myself, but you can be sure that I won't be doing anything as mad as diving in the Solent before tonight's game.

"The players know it will be a tough call without me resorting to that again."

Allen has had a mixed week since Brentford's big day at St Mary's ten days ago.

He added: "We went up to Hartlepool last Monday and couldn't train because of the snow. We had people pull out because of injury and illness and after losing 3-1 we didn't get back until 5 am on Wednesday morning.

"Then, on Friday, Mark Chap-man, a member of my coaching team, resigned. He's done a tremendous job in providing me with video compilations of players and he will be a big loss.

"But Saturday was a special day. The 3-3 draw against Wednesday meant we have achieved our first target for the season, the 51 points that should guarantee us our place in the division next year.

"And on Sunday night I wore my Brentford FC tie with pride when I was asked to appear on Match of the Day 2."