The Rangers keeper, Andy Goram, is facing a possible operation on a calf problem, while Bryan Gunn of Norwich is out until the end of the season. "Thankfully Jim's in great form right now," said Brown. "But his fitness will be a real concern to me over the next month.
Leighton, who will be 37 this year, won the most recent of his 61 caps at the end of last season in the Netherlands. He has been in superb form for Hibernian this season, and another comeback would underline his return to the top level five years after being dumped by the Manchester United manager, Alex Ferguson.
Leighton was axed for the 1990 FA Cup final replay against Crystal Palace with Les Sealey preferred, and the former Aberdeen player was relegated to reserve-team football before returning to Scotland with Dundee.
But the Hibs manager, Alex Miller, No 2 to Brown at international level, rescued him from Dens Park 18 months ago and has seen his faith rewarded.
Leighton's Hibs team-mate, Darren Jackson, is seen as the most likely candidate to step up from the B squad for the match with Russia. Jackson scored in Tuesday night's 3-0 victory over Northern Ireland, with Steven Tweed and Stephen Wright also on target.
"One or two players did their claims no harm, and another use for a B game is that you can eliminate one or two - although I won't name names," Brown said. "People like Paul Lambert, Rob McKinnon and definitely Jackson are in my thoughts."
The Hearts striker, John Robertson, who was named man of the match in the 4-2 Tennents Scottish Cup win over Rangers on Monday, has not been ruled out for a senior recall, although Duncan Ferguson of Everton, Bolton's John McGinlay, and John Spencer of Chelsea are ahead of him in the queue.
Scotland have another B game in Sweden on 10 October, when Brown will hope to try out several English-based players, such as Nottingham Forest's Scot Gemmill, Gerry Creaney of Portsmouth, and Chelsea's Craig Burley.
Before then, there is a two-match trip to Japan in May prior to the final European Championship qualifier of the season in the Faroe Islands on 7 June. Players from teams in the Scottish and English Cup finals will miss out, but the early exits of Aberdeen, Motherwell, Rangers, Leeds and Blackburn will help Brown's selection for the games against Japan and Equador.
Jackson yesterday admitted that he had deserved to wait for an international cap, seven years after being picked for the Scotland Under-21 squad. "It has been a long wait over the years, but it has been my own inconsistency which has held me back."
Jackson scored a stunning goal against Northern Ireland, and now the 28-year-old striker is in line for a place in the senior side, after being included in the squad for the last two qualifiers against Russia and Greece.
"It was a sensational goal from Darren. He was the one who looked to have an edge on all the other guys,' Brown said. "I'd have no hesitation in using him at full level. If he is the form striker we will use him, and he seems to have an appetite for the big occasion."Reuse content