Elsewhere, Algerian Madjid Bougherra is a doubt for Sunday's North African derby at home to Morocco.
But, although he held off the challenge of Madjid Bougherra, the striker's shot was collected by McGregor.
Rangers were without Madjid Bougherra in Perth after the central defender returned late from international duty with Algeria.
After eight minutes, Russel found a yard in the Algeria box but headed wide under pressure from Madjid Bougherra.
With Sasa Papac and Madjid Bougherra still missing through injury injury, manager Walter Smith continued to experiment with striker Lee McCulloch in defence.
Charlie Mulgrew was dismissed for an alleged head-butt on Kyle Lafferty before Rangers Madjid Bougherra saw red for a challenge on Jamie Langfield.
Rangers are without defenders Madjid Bougherra and Andy Webster, while midfielder Maurice Edu and strikers James Beattie and Nikica Jelavic are all still missing.
Madjid Bougherra cracked in an angled volley on 26 minutes to brighten up what was a scrappy match, dogged by sloppy play from both sides.
Madjid Bougherra took advantage of poor marking to slam in the first goal for Rangers as they cruised to a 2-0 victory at Easter Road.
Madjid Bougherra and Steven Davis were stand-outs for Rangers last season.
Smith showed faith in 18-year-old Danny Wilson, who started in central defence in place of Madjid Bougherra, who had joined Algeria's African Cup of Nations squad.
The 19-year-old played on the left-hand side of a three-man central defence and ventured forward to meet Madjid Bougherra's cross and head Rangers ahead on 24 minutes.
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With Madjid Bougherra's intermittent absence this season through injury or international duty with Algeria, Wilson has seized the opportunity to partner David Weir in the centre of defence.
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Rangers centre-back Madjid Bougherra and his usual replacement in that position, Lee McCulloch, had succumbed to flu so Papac moved into the centre of defence with David Weir.
As the first half came to close, a free kick from Whittaker found Madjid Bougherra beyond the back post but the big defender headed over from a tight angle.
In the same match, which Rangers won 2-1, Dougal also red-carded Madjid Bougherra after the defender caught Aberdeen goalkeeper Jamie Langfield with his boot while challenging for the ball.
Fellow centre-half Madjid Bougherra is also relishing the prospect of his first taste of the Champions League after ending an impressive debut season at Ibrox with a league winner's medal.
Meanwhile, Liverpool have had a bid rejected for teenager Danny Wilson, while fellow central defender Madjid Bougherra and midfielder Kevin Thomson have all been linked with moves away from Ibrox.
But Rangers soon moved ahead as Madjid Bougherra ventured forward and played a delicate one-two with Naismith before pulling back for Miller to turn home his 21st goal of the season.
Brown and Rogne had made way for Ki and Loovens respectively and Rangers made an enforced change of their own when Madjid Bougherra came off to be replaced by Kyle Hutton.
Rangers players El-Hadji Diouf and Madjid Bougherra have also been informed that they will be referred to the SFA's disciplinary committee on 12 April, for 'misconduct of a significantly serious nature'.
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Buoyed by the early breakthrough, Rangers looked for a quick second and Madjid Bougherra's pass was flicked up and volleyed towards goal by Kenny Miller, forcing Smith to make an impressive save.
The first was rather fortunate when Madjid Bougherra burst down the right flank before whipping a dangerous cross into the box that goalkeeper Jamie MacDonald just managed to tip over the crossbar.
Mendes became the third Rangers player to be sent off this season, following defender Madjid Bougherra in the midweek Champions League draw with Stuttgart and midfielder Kevin Thomson against Hearts on August 23.
Rangers had three players - Steven Whittaker, Madjid Bougherra and El Hadji Diouf - shown red cards, while Lennon had a heated exchange with opposition assistant manager Ally McCoist on the touchline at the final whistle.
There could be player suspensions for Smith to deal with as well after Madjid Bougherra and El Hadji Diouf were ordered to appear before the SFA's disciplinary committee following their actions in the same Old Firm derby.
Meanwhile, in Group G , Rangers defender Madjid Bougherra made amends for his red card in the Scottish Premier League at the weekend by grabbing the equalizing goal in a hard-fought 1-1 draw at Bundesliga side Stuttgart.
The flashpoint involving the two men followed a match that was pockmarked by red cards for Rangers players Steven Whittaker, Madjid Bougherra and El Hadji Diouf, 13 cautions and a series of angry scenes in the Celtic Park technical areas and tunnel.
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After Rangers' Madjid Bougherra had been booked early on for a late lunge on Ian Murray, Chris Hogg's mistake allowed Pedro Mendes to put Kris Boyd through on goal but Hibs captain Rob Jones got back to make a vital saving tackle.
But they got off to the worst possible start when keeper Kasper Schmeichel raced out after a long pass from Madjid Bougherra only for Charlton striker Varney to beat him to it and lob the ball into the empty net from 20 yards.
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