Former Celtic striker John Hartson has lamented the manner of the Parkhead side's defeat in Russia against Zenit St Petersburg.

A limp 3-0 defeat has closed the door on Celtic's European involvement for the remainder of this season but after witnessing the energy of the opening leg, Hartson believes that Brendan Rodgers' side badly let themselves down.

Goals from Branislav Ivanovic, Daler Kuzyaev and Aleksandr Kokorin at the Krestovsky stadium eased Roberto Mancini’s side into the last-16 courtesy of a 3-1 aggregate victory.

And Hartson was bitterly disappointed with the performance on the night.

The BT Sport pundit said: “I was quietly confident going into the game but the players have gone and let themselves down. It was a very under par performance from Celtic.

“They never got going, the one thing that will disappoint the manager is the manner. Great teams can get beat but it’s the manner - conceding from a set piece after seven minutes and players switching off and not carrying out their roles.

“Zenit are a good side, not a fantastic side.

“I thought Celtic would get a goal but they never started to get going until they were 3-0 down.

“They were brilliant last week but it was just poor, poor management - I mean the players - in the way they went about it.”