Sol Campbell (toe), Younes Kaboul (ankle) and John Utaka (hip) were all absent from the weekend victory over Blackburn.
The trio were also unable to train on the Fratton Park pitch afterwards along with the substitutes and those in the squad who didn't feature in the 3-2 success.
They are now facing a race against time to declare themselves fit enough to take a seat on the plane to Hannover tomorrow.
Campbell has the best chance of being available, having started running last week following his toe injury.
The Blues skipper has missed Pompey's last four matches, during which time they have shipped in six goals.
Natural replacement Younes Kaboul is also struggling, having picked up an ankle injury during the AC Milan draw.
Noe Pamarot is on stand-by to replace both at the centre of defence, although Hermann Hreidarsson is also an option.
Utaka has an outside chance as he continues to progress in his recovery from a hip problem sustained against Hull.
Richard Hughes will be fine, however, having recovered from a kick in the foot he initially suffered at the hands of Mathieu Flamini against Milan.
The problem forced him to receive intensive treatment ahead of the Blackburn game, but he came through it with no further problems.
Meanwhile, Lassana Diarra remains on the sidelines as he continues his recovery from an ankle injury.
The French international is expected to be out for another three weeks as his rehabilitation is stepped up.
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The full article contains 290 words and appears in The News newspaper.