Ronny Deila has said that he does not know what to expect from Dundee United when the teams meet on Sunday.
Mixu Paatelainen became the new United manager last week and will take charge of his first match against the Bhoys.
"They have changed the manager so it's not so easy to say how they are coming into this game," Deila told reporters.
"There's always a change when the new manager comes in. The club has been through a difficult situation but they still have talent in the side.
"It's going to be a difficult game. They have to fight to get points and we need the points to stay top of the league so it's going to be an exciting match on Sunday."
Celtic are currently two points clear of Aberdeen in the Scottish Premiership table while United sit bottom with just five points from 11 matches.
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