Ospreys lock Alun-Wyn Jones will captain Wales in their RBS 6 Nations opener against Italy next Saturday (2.30pm, live on RTÉ Two).
Jones takes over from Sam Warburton, who will begin his comeback after two months out with a shoulder injury on the replacements' bench.
Elsewhere, Rhys Priestland has edged out Dan Biggar for fly-half duties, Jamie Roberts returns in midfield after missing this season's autumn Tests, Paul James replaces injured prop Gethin Jenkins and Luke Charteris fills the second-row vacancy left by suspended Ospreys forward Ian Evans.
It later emerged that Warburton could end up starting the Italy clash after Lydiate flew back to Paris on Tuesday morning.
Lydiate's partner is due to have a child, and the former Newport Gwent Dragons forward has returned to be with her.
The Wales squad has a day off on Wednesday, and it is not known at this stage whether or not Lydiate will take part on Saturday.
If he was to be unavailable, then the likelihood is that Warburton would be promoted off the bench and start in the number six shirt.
Wales: L Halfpenny; A Cuthbert, S Williams, J Roberts, G North; R Priestland, M Phillips; P James, R Hibbard, A Jones, L Charteris, A-W Jones (c), D Lydiate, J Tipuric, T Faletau.
Replacements: K Owens, R Bevington, R Jones, A Coombs, S Warburton, R Webb, J Hook, L Williams.
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