Royal Marine flanker Hayler is unavailable due to work, while second-row Holmes has university commitments.
Holmes has only missed one previous game this season, while fellow 20-year-old Hayler has started nine games in between Royal Navy rugby duties.
“It is a blow that they are both unavailable,” said Albion’s director of rugby Graham Dawe.
“But people are waiting for a chance to put the shirt on and challenge.”
Holmes’ absence is likely to open the door again for Dan Collier. Experienced lock Collier has started 12 of Albion’s 17 league games this season but he lost his place after missing the Hartpury College game just before Christmas with an infection in his hand.
Collier has come on as a replacement in Plymouth’s last two games after returning to fitness and scored his first try of the season last weekend against Hull Ionians.
Frenchman Gregory Sebastien would be favourite to fill Hayler’s spot. Sebastien has only made two starts for the club since moving to Brickfields in late September, but he has made an impression in recent games from the bench.
Dawe, meanwhile, says Cameron Thompson, James Penman and Tom Putt are all making good progress following injuries.
Flanker Thompson had been hoping to be fit for this weekend’s trip to his former club Fylde, but it looks like the game might come too soon for the Plymothian.
Thompson has not featured in Albion’s first team squad since November due to injury.
“He is getting close to fitness, but has not trained yet,” said Dawe. “He started four or five games in a row and did well, but he pulled his groin in training and that was compounded by another injury.”
Hooker Penman has not played since suffering a calf injury against Loughborough Students in December, while goal-kicking full-back Tom Putt has been out for longer with a problem with his heels.
Dawe said: “James Penman might be back next weekend or the weekend after and Tom Putt the beginning of February.”
Australian centre Marc Koteczky suffered a bruised shoulder last weekend in their defeat to Hull Ionians, but Albion expect him to be fit for the trip to Lancashire.