Moses is expected to miss the rest of the regular season with a fractured eye socket ahead of a do-or-die moment in the Eels' campaign.
Tenth-placed Parramatta face fellow top eight hopefuls Sydney Roosters on Friday before a trip away to Penrith and a bye to round out their season.
Win both games and the Eels can hope to play on in September, lose just one of them and it's curtains for last year's grand finalists.
"That's rugby league, it can humble you pretty quickly," Gutherson said.
"We're not giving up yet and we're going to go out there on the weekend and try and play the best footy we can and give ourselves a chance.
"Mitch the leader of our team and you'd much rather have him in than out but that'll give someone else an opportunity and we have to go out there and win."
Daejarn Asi is expected to partner Dylan Brown in the halves with Reagan Campbell-Gillard and Maika Sivo both returning from suspension to boost the Eels' fading finals hopes.
Gutherson underlined that injuries and suspension had been a running theme of the Eels' season but said they could take confidence in how close they had pushed the Roosters and defeated Penrith earlier in the year.
"When we play the footy we want to play, we can beat anyone - Roosters, Penrith, (whoever)," Gutherson said.
"We know we can challenge them but it's about possession and holding the ball and we haven't done that the last couple of weeks and teams have made us pay.
"We've had a lot of things not go our way but there's no excuse, we go out there to win and we will be fighting until the last minute."
