McGuire left the field against Widnes two weeks ago after suffering from a knee injury.
But captain Sinfield says McGuire is irreplaceable in the Rhinos team.
He said: “What Danny gives us, there is no other player in the competition what he can do so we can’t replace him. We just need to find another way of integrating a different type of player into the squad and hopefully we can do that, whether it’s Steve Ward or Rob Burrow
“Danny has been great for us and for me to play along side him in the halfs. We have strung up a great relationship, and to get injured a fortnight before Wembley is tough to take, obviously for Danny, and for the team and myself.
“We know what it meant to Danny so its one of those set backs that one of those pieces of adversity which are thrown at you from time to time and hopefully we are good enough to overcome that.”
Sinfield believes that the biggest challenge facing him in Saturday’s final is creating cohesion between himself and whoever will take up McGuire’s role in Brian McDermott’s starting 13. Sinfield believes the decision will be between Steve Ward and Rob Burrow.
Sinfield said: “The key thing is that they play the best they can for the team, and we’ll all be happy with that. Stevie played there at the weekend and did a fantastic job for us. So whether its Stevie or Rob this week, they will roll their sleeves up and hopefully as a team we can respond to their qualities.”
Sinfield says he has no preference as to who will play along side himself. He simply wants to go out there and perform to the best of his ability. He has praised both Burrow and Ward for their efforts in getting Leeds ready and into the form they are in now.
Sinfield said: “Rob has been doing a good job at hooker this year and obviously we can have Shaun Lunt as another number nine.
“Stevie has been great but hopefully in these next few days we can gel a combination together and try to get things going.”