But after an extended lay-off, the 29-year-old star admits he is sick of training and ready to hit the ground running at the Liberty Stadium.
Byrne said: "I've been back in training for a few months now and I'm feeling in good shape. There's no injury problems or hangover from the tour.
"I've put in the hours on the training ground and the coaches have put me through my paces - the game can't come soon enough now.
"It's nice to have a good break but there's only so much training you can do. I'm ready to play."
Byrne lines up for the clash with the European champions alongside fellow Lions Tommy Bowe and James Hook with Alun Wyn Jones named on the bench.
And he hopes his impact can change the Ospreys' fortunes following last weekend's 20-16 defeat to Ulster.
Byrne said: "Leinster are a formidable side and even without their Lions, they've got real strength in depth and quality.
"Every team loses in sport but we know what we're capable of and have the belief in our own ability to win."
Ospreys: L Byrne, T Bowe, J Spratt, A Bishop, N Walker, J Hook, J Nutbrown; D Jones, H Bennett, C Mitchell, I Gough, J Thomas, J Collins, T Smith, M Holah
Replacements: R Hibbard, P James, AW Jones, F Tiatia, M Phillips, D Biggar, G Owen