The Scottish champions after facing a tougher defence of their domestic crown this season than they have grown accustomed to in recent years.
That is expected to see Brendan Rodgers dip into the recruitment market and bolster his squad.
Deals are already being mooted for the likes of Paris Saint-Germain forward Timothy Weah, but Nicholas believes greater experience is required and should be sought within the Premier League ranks.
The former Bhoys striker told the Scottish Daily Star: “A striker has to be a priority.
“Brendan could try to get Jermain Defoe in from Bournemouth or Christian Benteke from Crystal Palace.
“He has been poor at Palace but he would score goals for fun up here. If Celtic are serious about retaining the title then they need proven players to hit the ground running.
“I would also target a keeper. Craig Gordon’s days at the top are numbered and I am not convinced Scott Bain is his long-term replacement.
“He could also push into the England squad and add real value so now’s a good time to make a move for him.”
Having offered up potential targets at opposing ends of the field, Nicholas also feels that a proven centre-half currently on the books at Stamford Bridge could be a useful addition.
He added on a man whose contract continues to run down at Chelsea: “Why not bring in Gary Cahill on loan?
“He is on big wages but it would be worth the gamble to keep the likes of Filip Benkovic and Jozo Simunovic right, especially if Dedryck Boyata is sold.
"It might be a small price to pay if it helps seal another treble!”