John Hartson believes former club Celtic are favourites to pip Rangers to the Scottish Premier League title but feels there could yet be an upset.
"Celtic must be favourites. You can see them winning them all their games but there are always a couple of twists and I sense there may be another," he said.
"Very seldom do the Old Firm games decide where the title goes."
Rangers, with four games to play, lead Celtic by a point but their old rivals have a game in hand away to Inverness.
Sunday's Old Firm goalless draw at Ibrox means Neil Lennon's side hold an advantage over Walter Smith's Rangers: if Celtic win their five remaining league games, they win the championship.
But the former Wales international striker warns that the pressure on the players can cause strange things to happen on the field.
He told BBC Radio Scotland: "Who would have seen Rangers losing to Dundee United at home? And Celtic went to Motherwell and lost.
"Tension is a massive word in sport. You see snooker players miss simple shots.
"Both the Celtic and Rangers players know now that if they slip up they can let the other team in.
"The players will obviously feel the tension. There is not a lot between the two teams but Celtic have hit a bit of good form at the right time."
Hartson recalled the final day drama of season 2004/05 when Scott McDonald's goals at Fir Park, combined with Nacho Novo's strike at Easter Road for Rangers against Hibernian meant that the SPL trophy headed to Ibrox.
"We have seen it in the past," said Hartson of the effects of pressure.
"I played in that game at Motherwell where we were 1-0 up with two minutes left and Scott McDonald scored two goals right at the death and we were all devastated after that.
"I have had the experience of one minute having the title in your hand and the next minute it being taken off you."
Hartson admitted to tipping Rangers for the title at the start of the season, believing their "know-how, more experienced players and it being Walter's last season" would give them the edge.
However, he praised Lennon for the way he has guided Celtic to a possible double in his first full season as manager.
"He divided a lot of opinion at the start," he added.
"But he has brought in some very good players, gelled a team together and they all love working for him.
"He's an intelligent lad and he knows were he wants to go in the game.
"He is living the dream - growing up a Celtic fan - and he has done very well.
"Being totally honest, I think the Rangers team is a lot weaker than the team I played against. (Stefan) Klos, Arthur Numan, Lorenzo Amoruso, Craig Moore, Barry Ferguson, (Shota) Arveladze, (Ronald) de Boer - you had real top-class players.
"The Rangers side is not as strong as they were but that's where we are in the modern game.
"I think in five or 10 years' time, with a bit of investment, Rangers will get back to where they were in terms of seeing these superstars and so will Celtic."