Albion will be without Bobby Zamora for at least two weeks after he suffered knee ligament damage in Saturday's 2-0 home defeat by Norwich.
Zamora was due to have a scan, but the injury settled down over the weekend and he was sent for an x-ray instead.
Boss Martin Hinshelwood confirmed: "It's a medial ligament strain. We are probably looking at two to three weeks. It's a bit like Jonesey's (Nathan Jones), but not as severe.
"In the end we didn't have a scan. It settled down a bit better on Sunday and we just had it x-rayed."
Zamora looks certain to miss the Bank Holiday fixture against Walsall at Withdean and the south coast derby at Portsmouth on August 31.
He will also probably be ruled out of the England under 21's friendly against Yugoslavia at Bolton on September 6, although he may not have been selected in any case as Albion are at Millwall the following day.
Albion's prolific hitman sustained the injury after a challenge with Nowrich defender Darren Kenton.
Hinshelwood said: "It was an innocent thing, a block. Perhaps Bobby tried to nick it rather than going and winning it and he just got caught."
Jones strained a knee ligament in the pre-season friendly against Bognor and has been out for nearly a month.
Norwich won with second-half goals by Paul McVeigh and Clint Easton after Zamora limped off.
Canaries chief Nigel Worthington said: "Bobby's a handful. He's a good player and that's why there is a lot of Premiership interest.
"When one of the opposition's better players goes off it's a sigh of relief.
"Brighton had a terrific start with an excellent win at Burnley and a great draw against Coventry.
"They have got to keep digging in and battling away. It's about everybody sticking together, the supporters as well, because their help is a big thing for any team."
Shaun Wilkinson made his full League debut up front for the Seagulls, with club captain Paul Rogers ruled out by illness.
"I enjoyed it very much," said the 20-year-old. "It was disappointing to lose, but I was happy to start and do reasonably well.
"Norwich are going to be there or thereabouts again, so it was tough."
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