Shearer, the pounds 15m Newcastle striker, had an operation yesterday to repair damaged ankle ligaments after being carried off after suffering the injury seconds from the end of Saturday's Umbro International tournament match with Chelsea at Goodison Park.
He was rushed by ambulance to Liverpool's Fazackerley Hospital where the injury was diagnosed and was transferred to a Newcastle hospital to undergo surgery yesterday morning.
Dalglish said: "He has had an operation to repair torn ligaments and without putting an exact figure on it, he will be out for a wee while. It will be months rather than weeks, but exactly how long we don't know yet."
Newcastle go into the new Premiership campaign without him, and he must be considered doubtful for England's remaining World Cup qualifiers against Moldova and Italy. England meet Moldova at Wembley on 10 September and then face Italy in Rome on 11 October.
Glenn Hoddle, the England coach, is abroad on holiday at the moment, but a Football Association spokesman, Steve Double, said: "Obviously it's a terrible blow for England, Newcastle and Alan himself.
"Glenn is on holiday abroad at the moment but he'll be back by the end of this week and he'll receive a report on Alan's condition as soon as possible.
"It's good to hear that Alan's operation has been a success. He's a player of enormous physical and mental strength and a quick healer from operations. We wish him a speedy recovery."
Shearer's lengthy lay-off raised doubts about Ferdinand's move to Tottenham, but the club fought off a last-ditch attempt from Newcastle to hold on to Ferdinand.
In the end, it was too late to stop the 30-year-old England striker joining the club he supported as a boy in a move which sees him team up again with his former manager, Gerry Francis: the pair were formerly together at Queen's Park Rangers.
Ferdinand met Alan Sugar at the Spurs chairman's Essex home yesterday afternoon and agreed personal terms. Sugar issued a simple statement which said: "Tottenham Hotspur and Les Ferdinand have agreed terms and he is now formally a member of the Spurs squad."
The club will unveil their record new signing at a press conference at their training ground this afternoon.
Spurs have been in desperate need for a striker following the sale of Teddy Sheringham to Manchester United for pounds 3.5m, and the news that Chris Armstrong will miss the start of the new season with an ankle injury.
Ferdinand joins former Newcastle team-mate David Ginola at White Hart Lane after the Frenchman made a pounds 2m move earlier this month.
The double signings have made a pounds 8m dent in a transfer fund of pounds 20m which Sugar has made available to Francis.
But the Spurs boss is still determined to strengthen his squad before the start of the new campaign and is scouring Europe for fresh talent.Reuse content