Gary Warren believes the spirit and belief of his new Inverness team-mates can ensure Celtic are given a tough test in Saturday's Clydesdale Bank Premier League clash.

The 28-year-old, a summer signing from Newport, helped Caley Thistle to a 2-2 draw at Tynecastle last weekend having been two goals down at half-time.

"You look at last Saturday and the way we performed last week, down to 10 men, the boys really had to stick together and showed true fighting spirit," said defender Warren.

"It was encouraging last week to come away from a difficult ground to get ourselves a 2-2 draw.

"Now, the boys are really looking forward to the test on Saturday.

"I think if you look at the boys we've got in the changing room, there is always belief.

"I think we've got so much energy and a youthful side, going down to 10 men, I don't think fazed us, to be honest.

"We were more determined to get a result, so in terms of the belief we have got in the side, it's a credit to the boys last week."

Neil Lennon admits his team selection for the trip to Inverness will be based on making sure there is no mistake in next Wednesday night's Champions League play-off clash with Helsingborg at Celtic Park.

The Hoops boss confirmed on Friday that Joe Ledley is out for two weeks with a groin injury while fellow midfielder Beram Kayal could be out for a month with an ankle complaint.

Daryl Murphy (hamstring), Dylan McGeouch (broken jaw) and Anthony Stokes (ankle) are already out and could be joined on the sidelines by Thomas Rogne (ankle), Scott Brown (hip), Georgios Samaras (thigh) and Kris Commons (ankle) if Lennon believes that is what is needed to make sure they are available for the second leg in midweek.

Celtic look to defend the 2-0 first leg lead against the Swedes which would take them in to the lucrative group stages of the Champions League for the first time since season 2008/09.

The Parkhead boss said: "The squad is a bit stretched again and there are a few bumps and bruises from Tuesday night and we will have to change the team a little bit.

"Rogne, Brown, Samaras and Commons are doubts. They are not too bad but they will struggle for Inverness I would imagine.

"I wouldn't look at it that way (giving them the day off) but we want to have our best team on the pitch on Wednesday night and if that means we can't take a risk with them, we won't.

"Joe has a grade one groin injury and he will be out for a couple of weeks and Beram has had a reaction to his other ankle (to the one which was operated on) and he will be maybe three to four weeks.

"The injuries aren't majorly concerning, particularly Joe's injury.

"Joe has been one of the best signings since I came to the club, and so consistent, he is a big loss to us.

"Beram is a little bit of a worry because it is his other ankle which is giving him bother.

"It is unfortunate. The midfield is probably the strongest department at the club.

"We have Victor Wanyama to come into the squad and we have options."

Inverness CT squad: Esson, Reguero, G Shinnie, Meekings, Warren, Raven, King, Pepper, Draper, A Shinnie, Ross, Morrison, Doran, Laing, Polworth, Sutherland, McKay, Oswell.

Celtic squad: Forster, Matthews, Lustig, Wilson, Mulgrew, Izaguirre, Rogne, Forrest, Brown, Samaras, Commons, Wanyama, Bangura, Twardzik, McCourt, Hooper, Zaluska, Keatings, Chalmers, Watt.