Leigh Griffiths has been sensational for the Scottish Premiership side this season but Walker is concerned about the lack of depth.
Ronny Deila will be leaving the Bhoys at the end of the season. And while the Norwegian led the club to their fifth Scottish Premiership crown in a row, there are some concerns about whether the squad is strong enough to be as dominant next season when the top flight looks set to become much more competitive.
And Walker - who enjoyed two spells with the club during his playing days - believes that it is up front that Deila's replacement needs to look to strengthen first.
"The manager will have to come in, assess the squad," he told Sky Sports.
"He'll have to sign a striker because he can't always rely on Leigh Griffiths. If he was to pick up an injury, Celtic would be really struggling."
As Walked alluded to, Leigh Griffiths has been sensational this term. His tally of 30 league goals has been hugely important to Celtic's success this season.
But if he was to pick up a knock that kept him out for a considerable length of time, it is unlikely that his replacement would be capable of getting close to that kind of strike-rate.
Carlton Cole and Colin Kazim-Richards have both had their bright moments since joining the side, but have not done anything that suggests that they would be capable of leading the line on a regular basis for a title-winning team.