Merson, who was named Nationwide Player of the Month yesterday, suffered an ankle injury in the 3-0 midweek win over Tranmere and faces a fitness test before today's match at Birmingham. Nigel Pearson is also doubtful, but Gianluca Festa returns after a two-match ban.
Birmingham's new pounds 1m striker Dele Adebola is on stand-by to make his debut and Martin O'Connor and Simon Charlton hope to return after injury. Steve Robinson starts a two-match suspension.
Portsmouth fans are planning a ticker-tape welcome for US property tycoon Vince Wolanin when he attends today's home game against Nottingham Forest before continuing takeover negotiations with the club's chairman, Martin Gregory. Supporters have promised a "razzmatazz extravaganza" with 4,000 cards being printed with the Stars and Stripes and the slogan "Wolanin's here today - wave the flag and let's make him stay".
Talks between Wolanin and Gregory fell through last week after the chairman insisted on receiving more than the pounds 2m that the American and his business partner, Brian Howe, were reported to be offering.
There is also friction in the dressing-room at Pompey, with Alan Ball, the manager, criticising Paul Hall and Fitzroy Simpson for missing a third of Portsmouth's season in their quest for international success with Jamaica.
Ball is furious that the British-born pair, who are each paid around pounds 250,000 per year by their club, are missing so many matches through their Jamaican commitments. "We are paying them to play in the World Cup, not for us. Portsmouth isn't the important thing in their lives any more," Ball said. "All we are concentrating on here is this club beating relegation - but we've got two players who are away playing for places in the World Cup."
Hall and Simpson are now taking part in the Gold Cup competition in America and may not be back in England until 28 February.
John Aloisi and Mathias Svensson could be recalled alongside on-loan striker Steve Claridge, while goalkeeper Aaron Flahavan is on standby to replace Alan Knight, who has flu. David Hillier is fit again, but Andy Thomson is suspended while Andy Turner is injured.
Dave Bassett, the Forest manager, is waiting on the fitness of Scot Gemmill, who missed last week's 3-1 defeat by Oxford with an ankle injury and will face a late fitness test.Reuse content