O'Driscoll left the field early in his Leinster team's victory over Glasgow on Saturday and the 34-year-old centre was unable to travel to London for the squad's first get-together in London on Monday.
"Brian has been told to stay off his feet for 48 hours. It's a back problem that comes and goes," said Gatland, seemingly unfazed by the issue.
"It normally takes a few days to relieve the pain. We will keep our fingers crossed he is able to play in the two Leinster games that are coming up."
Leinster face Stade Francais in the Amlin Challenge Cup final in Dublin on Friday before facing Ulster in the RaboDirectPro 12 final on May 25.
O'Driscoll is the only survivor from the Lions' last tour of Australia in 2001, when he scored a memorable try in the first test of the 2-1 series defeat.
He would be devastated to miss this final shot at victory with the combined team having had his 2005 New Zealand tour, when he was captain, cruelly cut short by injury after being spear-tackled in the opening minutes of the first test and also ending on the losing side in 2009 in South Africa.
O'Driscoll was well advised to steer clear of Monday's kitting out session as even the healthiest of backs would be put under strain by the mountain of gear, in every combination of colours, issued to the squad at the historic Syon Park House in west London.
He, and another 13 squad members involved in Amlin, RaboDirectPro 12 and Premiership finals, will miss the first two training camps in Wales and Ireland, giving the rest of the squad a head-start in catching the coach's eye.
"Ironically, those players not in the finals will be in a better position in terms of preparation for the tour and it does put the other guys at a bit of a disadvantage," Gatland said, confirming that the absentees would be unlikely to be considered for the opening tour match against the Barbarians in Hong Kong on June 1.
"The team that plays the Barbarians should be in reasonable shape in terms of their preparations in the next couple of weeks.
Gatland said the Lions have a "standby" list of around 40 names - their details already with officials to ensure a smooth passport and visa passage should they be called up for the inevitable injuries.
The New Zealander, on sabbatical from his regular job as Wales coach, said, however that it was pointless to worry about injuries for players to try to protect themselves.
"We are preparing for the fact a couple of players may pick up injuries that affect their ability to tour," he said.
"It's tough for the players as they know a few days after a big game they are on the plane and there's a bit of trepidation about not picking up injuries.
"But if you go in with that attitude and try and look after yourself there is more chance of picking up an injury.
"Players are going to go into the finals giving it their all, and I wouldn't want it any other way.
"My advice is for them to play their normal game."