Bullard joined Hull in a £5million move from Fulham last Friday but has since been suffering from a virus.

The 30-year-old midfielder should still make his Tigers bow at former club West Ham in the Barclays Premier League, but boss Phil Brown admits his involvement could be curtailed.

Brown said: "Unfortunately Jimmy has been under the weather.

"He will certainly play a big part, because he wants to play. He wants to play for this club and he wants to play against his old club.

"That is a recipe for success as far as I am concerned.

"I think adrenaline will carry him through but adrenaline can only take you so far and then you run the risk of fatigue, and then injury.

"Jimmy will play a big part but whether that is at the start or the end remains to be answered. I think 90 minutes is going to be too much for him."

Because of his illness, Bullard only made his first appearance at training today but Brown believes he has already given the squad a lift.

Brown is hoping the introduction of the combative former Wigan player can kickstart a league campaign that has faltered of late.

Hull have won just one of their last 13 league games and lost their last five.

Brown said of Bullard: "Today he was on the training ground for the first time and he was outstanding, a different class, a breath of fresh air to everybody.

"He plays football the right way, even with the circumstances we have got to suffer at the moment with the training ground knee-deep in mud.

"Hopefully that will be infectious on the squad in these pressure moments."

Hull beat West Ham 1-0 in October amid a run of four straight wins and Brown believes the Upton Park return comes in a crucial week for his side's campaign.

The Hammers clash is followed on Saturday by a visit from struggling West Brom.

"This was always going to be a big week," said Brown, whose mood has been lifted by progress to the FA Cup fifth round.

"There are a number of massive games between now and the end of the season, there are games you earmark as potential ones you can get something from.

"I have said that all season and I would put these two in that category."

Bullard's arrival was the third of the January transfer window at Hull, coming after the permanent signing of Kevin Kilbane and the loan capture of striker Manucho.

In addition, defender Kamil Zayatte has also been signed on a permanent deal after an impressive loan and Brown claims he may not be finished there.

He said: "I dare say we will be sitting in front of press conferences before the deadline closes - how many I can't say.

"I'm pleased with the squad but there is still a bit of movement to go.

"Is there money left, is there the possibility of bringing in another couple of players? The answer to all that is yes.

"There is a bit of business to be done by a lot of Premier League clubs but the most exciting thing to me would be to get six points this week."