The former Hoops striker-turned-pundit fears Rodgers may feel he has taken the side as far as he can, and writing in a national newspaper, said: “Celtic announced earlier this month that they have a whopping £30m in the bank.

“They may be cash-rich in Scottish football terms, but they proved once again they are paupers on the European stage as they went out of the Europa League with a whimper.

• READ MORE - Zenit 3-0 Celtic (3-1 agg): Rodgers’ men crash out of Europe

Brendan Rodgers lambasted his defence after the 3-0 reversal in Russia. Picture: SNS Group

“The manner of their defeat in the Krestovsky Stadium has me concerned that Brendan Rodgers may soon start to question his long-term future at Celtic.”

Despite leading 1-0 from the first leg in Glasgow, Celtic conceded an early goal in St Petersburg, before going down 3-0 to Roberto Mancini’s side.

Nicholas added: “I’m concerned that Brendan will now start to question just how much further he can take this side.”

• READ MORE - Five things we learned from Zenit 3-0 Celtic

Charlie Nicholas wonders if Rodgers may quit Celtic. Picture: SNS Group

Despite leading Celtic to a domestic treble in his maiden season in the Parkhead hotseat, with no domestic losses, Celtic finished bottom of their Champions League group last season and only just scraped into the Europa League knockout stages this season.

From eight European ties this season, Celtic have registered just two wins - against Anderlecht in Belgium, and last week against Zenit - while losing six matches, including 5-0 and 7-1 reversals against Paris Saint-Germain.

Nicholas continued: “I wouldn’t be surprised if Rodgers is asking himself just how much progress his side has made, and whether he will receive the financial backing required to take them forward on the big stage.”

Brendan Rodgers '˜could quit Celtic' after Zenit loss, claims pundit