Albion loan star Steve Sidwell is set to complete a permanent move to First Division rivals Reading today.
Sidwell missed the Seagulls' 3-1 exit from the FA Cup at Norwich last night to have talks with the Royals.
Parent club Arsenal have accepted Reading's offer of a £75,000 down payment for the free-scoring midfielder, which will rise depending on appearances and other factors such as the Berkshire club's possible promotion to the Premiership.
The Argus exclusively revealed Reading's interest last Friday. Sidwell had transfer talks last week with Stoke and Albion made a counter bid to sign him permanently, but boss Steve Coppell is resigned to losing him.
Coppell said: "We were all set to have him with us at Norwich, but after discussions with Arsenal they were quite adamant that he wasn't to play.
"I felt after Saturday's game against Coventry, where he was the best player on the pitch by far, that if anyone is watching him they are going to look to try and sign him.
"It's a massive blow for us. We were just looking good in a three game spell and he was the cutting edge for us. To lose him leaves a big hole."
Reading coach Kevin Dillon said: "We've come up against Steve on many occasions when he has been on loan at Brentford and Brighton.
"He tackles, wins headers and we've been watching him for a long time so it's true we're trying to sign him."
Fellow Arsenal loan signing Graham Barrett may have talks with Preston today over a permanent move.
Coppell said: "I spoke with his agent last week and he told me the earliest he would consider going to Preston was after the Norwich game. I don't know if he had planned to talk to them."
Albion suffered another major blow in the 27th minute of last night's tie when Michel Kuipers was forced off by a recurrence of right-thigh trouble.
Youngster Will Packham took over but Coppell will today launch a hunt to sign another keeper ahead of Saturday's visit by leaders Portsmouth.
"Michel had pulled his kicking muscle and I imagine he will be out for some time," Coppell said. "I have only got one goalkeeper now and I would like to have the comfort of a second.
"I will be on the phone and I am hopeful of signing one before the weekend."
Three goals in the last 34 minutes by Phil Mulryne (two) and Paul McVeigh condemned Albion to their 18th defeat of the campaign in all competitions after Robbie Pethick had given them a 48th minute lead.
Norwich are now at home to Dagenham and Redbridge in round four a week on Saturday, when Albion will be without a match.
Their exit wrecked a dream reunion for former Albion forward Junior McDougald, who scored Dagenham's second in a 2-0 replay win over Plymouth.
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