The message from Mark McGhee could not have been clearer.

Heads are going to roll and players who want to avoid decapitation must buck their ideas up.

McGhee did not mince his words after his first home League game in charge resulted in Albion's worst ever defeat in their four and a bit seasons at Withdean.

"A lot of shouts in the stand were 'Come on McGhee sort this out,' and I am going to sort it out," vowed the no-nonsense Scot.

"I've seen a lot now. I think I know enough. I am saying to the supporters it is going to be sorted out as quickly as possible.

"From the players' point of view I have said to them anyone that wants to be part of what ever is going to happen here over the next couple of years needs to do better than that.

"We lacked aggression. I would even criticise the commitment at times.

"Most of the players can do better and they will still have the opportunity, but things are going to be sorted out and there are going to be casualties.

"It is up to the players to decide who is prepared to get on with it and who is going to fall by the wayside."

Reputations count for nothing as far as McGhee is concerned. He will dismantle the established order as he sees fit.

The process is already well under way. Only two players signed by Micky Adams, Danny Cullip and Richard Carpenter, were in the starting line-up on Saturday.

Nathan Jones and Paul Watson were not even in the squad, although nobody has been given the boot for good just yet.

McGhee said: "I have got to look at everyone and be fair to everyone.

"I don't know all the players inside out and those players have not been discarded by any means, particularly after a performance like that.

"They are maybe the ones that will get a chance again now. I've got to learn about the players, to tweak it and change it and move it around to find out who are the best and what the best combination is.

"I've learned that the squad is not strong enough, not physical enough and not aggressive enough and that is something I will now be trying to put right."

Given the limited funds at his disposal, it makes sense for McGhee to sell Michel Kuipers to Hull if it gives him scope to bring other players in.

It is impossible to keep two established keepers happy at this level and McGhee has decided Ben Roberts is his No. 1.

Roberts was not at fault for any of City's goals, three of which were headers from crosses. "When balls go into the box and you don't defend then it shows a lack of aggression," McGhee said.

"When the ball was in their box they were close to us, they were interfering with our centre forwards. Our players trying to attack crosses were being manhandled, which is what defending is all about.

"In our box people had space, there was no physical contact. You have got to get tight to people and defend. We did not look to be able to do that and that is unacceptable.

"We couldn't cope with a team who are physically strong and have pace and strength all over the field, which in a way was similar to the way we failed last week at Lincoln."

Bristol, rewarding Danny Wilson's adventurous selection, went ahead after 26 minutes with a classic counter-attack after clearing a free-kick inside their own area.

Christian Roberts released Luke Wilkshire through the inside right channel to slot his second goal in as many games.

It was 2-0 five minutes later when the fit-again Lee Miller, deputising for unwell top scorer Lee Peacock, scored with a free header from Kevin Amankwaah's right-wing cross.

Aaron Brown's header in off a post from another right winger centre by the impressive Amankwaah a minute before the break threatened a rout.

Miller gifted Albion a lifeline in first half stoppage time. He handled a Kerry Mayo corner and Leon Knight stroked in his 14th goal of the season from the resulting penalty.

The Seagulls dominated the second half without looking like scoring. Matt Hill put them out of their misery six minutes from the end with a header from a Wilkshire centre which Roberts got a hand to.

Bristol's last two goals contained an element of controversy. Knight was clearly fouled in the build up to the third and the linesman had his flag up when Hill headed in but quickly put it back down.

At least Albion's more spirited performance after the break offered some hope. It coincided with 18-year-old debutant Mark Yeates from Spurs being switched from the left to the centre of midfield.

McGhee's other signing Zesh Rehman, back for another month from Fulham, was replaced by John Piercy at half-time as part of the reshuffle.

"I thought Zesh was disappointing," said McGhee. "He needs to be more aggressive and get himself more involved in the game. Physically he needs to up the tempo.

"Mark Yeates was much better in the second half when he went into the middle. He showed what he is all about with his ability on the ball.

"I got a flavour of what I think he can bring to Brighton and I was quite pleased with that."

The flavour of the current squad seems less and less suited to McGhee's taste the more he sees of them. What began as evolution is gradually turning to revolution.

ALBION (4-4-2): Roberts (gk) 7; Mayo (lb) 5, Cullip (cd) 5, Knight (f) 6, Hart (rm) 5, Yeates (lm) 6, Carpenter (cm) 5, Butters (cd) 5, McPhee (f) 6, Hinshelwood (rb) 6, Rehman (cm) 5. Subs: Kuipers, Pethick for Hart (withdrawn 75), Piercy 6 for Rehman (withdrawn 46), El-Abd, Robinson for McPhee (withdrawn 83).

Scorers: Knight (45) penalty.

Bookings: Hart (24) dissent, Carpenter (71) foul, Piercy (88) foul.

BRISTOL CITY (4-4-2): Phillips; Carey, Hill, Wilkshire, Miller, Tinnion, Brown, Roberts, Coles, Amankwaah, Woodman. Subs: Butler for Woodman (injured 46), Burnell for Tinnion (withdrawn 69), Stowell, Matthews for Miller (withdrawn 87), Lita.

Scorers: Wilkshire (26), Miller (31), Brown (44), Hill (84).

Bookings: Amankwaah (62) kicking ball away, Miller (68) kicking ball away, Brown (78) not retreating.

Half-Time: Albion 1 Bristol City 3.

Attendance: 6,305.

Fan's View (Billy Phillips, aged 14 Lancing).

What a disappointment.

A season of promotion has now come down to talk of mid-table security and even a relegation dog fight.

We need to improve and fast if we want to stay in the promotion race.

Over the last few weeks something has changed.

Whether we blame it on the departure of Steve Coppell, injuries or something else it is still the same team that performed under Coppell but seemingly can't under McGhee.

If these performances don't improve there will be empty seats appearing and that plays into the hands of all those against Falmer.

It means we might not get a new stadium, still won't be able to keep top managers and players at Brighton and we will be in the same old situation.