Celtic legend John Hartson has urged Brendan Rodgers to strengthen the squad in two key areas before the transfer window slams shut on Thursday night.

The Bhoys have been in scintillating form since their return to action following the mid-season break in Scotland, after winning three games on the spin without conceding.

Both Oliver Burke and Timothy Weah have already opened their goal tally for the club after joining on loan deals from West Brom and Paris Saint-Germain, respectively, this month.

Despite their swashbuckling start, Hartson feels Celtic must strengthen in two more key areas to add some balance to the squad.

The former Bhoys striker has urged Rodgers to make some additions to his defence by roping in a right-back and central-defender before the end of the winter transfer window.

Hartson admits he has been surprised so far by Celtic’s lack of interest in strengthening in defence and insisted all the other areas are well covered at the moment.

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“One thing that has surprised me during this transfer window has been Celtic’s failure to strengthen the defence”, Hartson wrote in his column for the Evening Times.

“There are still a few days to go of course, so perhaps it is all in hand, but the centre of defence and in particular, the right-back position, need to be addressed.

“Perhaps Brendan Rodgers feels that Mikael Lustig can still do a job with Anthony Ralston providing cover, and that they are strong enough at the heart of defence with Filip Benkovic, Jozo Simuovic, Dedryck Boyata and Kris Ajer.

“I can’t say I agree.

"Two or three of those players won’t be at the club next season, and there are obviously the early European games to think about as well.

“We’re pretty well placed in other areas of the team, but I would really like to see these two areas addressed so that the new players coming in have time to bed in during the remainder of the season.”

Celtic could go six points clear at the summit of the Scottish Premiership table, if they win against St Johnstone at Parkhead on Wednesday.