|World Cup Qualifying Group F: England v Scotland|
|Venue: Wembley Stadium Date: Friday, 11 November Kick-off: 19:45 GMT|
|Coverage: Listen on BBC Radio 5 live, BBC Radio Scotland & BBC Sport app; live text commentary on BBC Sport website & app|
The Scots slipped to fourth in Group F after October’s setbacks against Lithuania and Slovakia.
But a victory over the English, who have not lost a qualifier since 2009, on Friday would draw Gordon Strachan’s side level with the top seeds.
“I think they just have to believe in themselves,” said Gallacher.
The Scots were held to a 1-1 draw at home by Lithuania before a 3-0 defeat in Trnava.
“I just think they went there and felt it was going to be easier than it was and that they’d win the game,” ex-Dundee United, Coventry and Blackburn striker Gallacher told BBC Scotland.
“They’ve had a rude awakening and hopefully that’s the kick up the backside that wakes them up that they’re not as good as they think they are at this moment.
“They’re going to have to lift it up a level again, and who better than to lift it up against than England?”
Gallacher, who was capped 53 times, was part of the last Scotland squad to reach a major finals – the 1998 World Cup.
The 49-year-old, who scored in the final qualifier against Austria at Celtic Park that sealed a place in France, thinks head coach Strachan has an important role in preparing the players psychologically for the game.
“However mentally he can get into the players, he has to try it,” said Gallacher.
“Whether it’s watching Braveheart, whether it’s watching an old game where you beat England at Wembley, these all give players inspiration and belief that they can do it.
“England at the moment don’t have a manager, they have a caretaker in Gareth Southgate, so they’re hobbling along as well.
“Sometimes it’s better to get the wounded animal while it’s limping and this could be an opportunity for Scotland.”
Gallacher started the first leg of the Euro 2000 play-off first leg against England – a 2-0 defeat at Hampden that ultimately began the Scots’ big tournament exile.
Although Gallacher picked up a booking that ruled him out of the 1-0 second-leg victory at Wembley, he has only good memories of facing the “Auld Enemy”.
“It’s brilliant, it’s what you want, Scotland against England,” he said.
“We were playing against team-mates and you wanted to be able to get that result, rub a little bit of banter on them and give them a bit of stick.”
Regardless of the outcome of the game in London, Gallacher wants to see Strachan continue in his role as head coach despite a record of only three competitive wins – against Malta and Gibraltar twice – since a victory over Ireland two years ago.
“If we keep chopping and changing managers and chopping and changing systems, I don’t think we’ll ever settle,” he added.
“As long as the boys put in the best performance that they can against England, don’t lie down, put in a performance that merits something and you can see that they’re working for the manager then I don’t see why we should take Gordon out of the equation.”