The midfielder's versatility has been evident in recent weeks, as he has come off the bench and been asked to perform in a number of different roles.
However, De Marcos - a regular in the team under previous boss Marcelo Bielsa - accepts not being a regular starter under current boss Ernesto Valverde.
The 24-year-old explained: "My role has changed - but the coach is counting on me.
"He knows how to lead the team well and it is not easy to enter the starting 11 because they are usually doing well."
The Basque side surrendered their unbeaten record at the new San Mames in their last home match against Espanyol, but bounced back to p ick up their first win in four games with a 2-0 triumph at bottom club Real Betis last time out.
The result maintained Athletic's four-point cushion over fifth-placed Villarreal and De Marcos knows the significance of victory against Granada, adding: "It's very important to win this match because doing so will require that our rivals win to keep up with us.
"This is what we have to think now because we just won't know until the end of the championship whether it has been a good or a bad season."
Despite losing their last four away matches, Granada have still picked up more points away from at Los Carmenes and currently occupy 13th position - five points and five places above the relegation zone.
Midfielder Fran Rico is a doubt for the visitors with a muscle problem which forced him off in the first half of the 2-1 defeat at Valencia last time out. His replacement at the Mestalla, Mohammed Fatau, is again poised to step in.
- Sports & Recreation
- De Marcos
- Marcelo Bielsa