The former Celtic striker made the suggestion following the Hoops’ embarrassing defeat to Paris Saint-Germain away from home in the Champions League on Wednesday evening.
Despite taking an early lead through star striker Moussa Dembele in Paris, Brendan Rodgers’s side went down 7-1 to Unai Emery’s side.
It was one of Celtic’s worst performances in Europe in recent years, as their backline failed to do much against PSG’s attacking prowess.
Former Celtic striker Hartson was following the match for BT Sport, and he suggested that for the Glasgow giants to compete in Europe, they need a defender.
Hartson said on BT Sport 3 on Wednesday evening (9:52pm, November 22, 2017) during the post-match coverage of PSG against Celtic: “For Brendan to improve Celtic in Europe, he will need a better quality of defender. They have to back him. The board have to back him to do that.”
Celtic have the strongest squad in Scotland, and they are going to win the Scottish Premiership with ease yet again this season.
However, for the Hoops to make an impact in Europe, they do need to address their issues at the back and have to stop conceding seven goals in a match even against the strongest teams.