Rangers fell to the second defeat of their German tour after shipping three second-half goals in a 3-0 defeat against Bochum.
Ally McCoist's men competed well in the first half following their 1-0 defeat by minnows Sportfreunde Lotte on Thursday, but they were exposed in defence after the interval.
McCoist, who has been trying to secure the return of Carlos Cuellar from Aston Villa to strengthen his defence, watched as a back four of Steven Whittaker, Kirk Broadfoot, the out-of-contract David Weir and Sasa Papac struggled against the German second-tier outfit.
McCoist started with the same team that lined up against Lotte despite Madjid Bougherra's return to the set-up amid ongoing uncertainty over the Algeria centre-back's future.
But, while the Lotte defeat came amid a raft of changes which ended with an inexperienced team finishing the game, McCoist kept a strong team throughout with only Neil Alexander, Kane Hemmings and John Fleck coming off the bench.
The game started slowly before Rangers goalkeeper Allan McGregor punched clear a curling effort from Denis Berger and a powerful strike from Slawo Freier.
Home defender Lukas Sinkiewicz headed just over but the Scottish champions improved and Papac got a header on target, although they could not carve out a chance before the break despite some decent possession.
Alexander came on at the break and soon tipped Freier's low drive wide before Nikica Jelavic shot weakly after breaking clear of the German defence.
The home side, who beat Aberdeen 2-1 in midweek, took the lead in the 64th minute when substitute Daniel Ginczek slotted past Alexander following Bjorn Kopplin's low cross.
Whittaker shot straight at the keeper after a good run but Rangers fell further behind with 16 minutes remaining when Mirkan Aydin broke clear and slotted home. Oguzhan Kefkir then hit Alexander's post before Anthar Yahia emphatically netted a rebound after the Rangers keeper had saved from Aydin in the 81st minute.
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