The D pairings were all different from preseason. Was it a factor? Hard to say.
Also, Garrison's penalty came on an outside in move - he was beat several times like that last season IIRC. Although he reportedly can play both sides, he himself has said he prefers the left side - obviously because he plays better there.
But putting Garrison back to the left side means either Weber or Corrado in the lineup, with either Alberts or Stanton as the 4th left/8th D. With Stanton and Corrado, avg. Age of the 8 is 26.1 (rounding each player to their draft year). Not bad at all and an organizational strength.