CELTIC manager Brendan Rodgers revealed on Saturday that the club will not bring in any more expensive marquee signings during the transfer window as the club’s business model doesn’t allow for it. The Northern Irishman was keen to point out that this doesn’t mean that there won’t be any more arrivals in Glasgow’s east end this month, just that fans shouldn’t expect to see fees like the £9 million Celtic shelled out for Odsonne Edouard spent this month.

Celtic have already brought in Timothy Weah and Oliver Burke in on loan from Paris Saint Germain and West Bromwich Albion respectively, and signed 22-year-old striker Vakoun Issouf Bayo for around £2 million. The club have also been linked with a couple of right-backs over the last week or two, notably Atalanta’s Timothy Castagne and, more recently, Olympiacos’ Omar Elabdellaoui.

Rodgers has spoken about the club’s need to have “more of an offensive threat” going into the second half of the campaign and until the likes of Weah and Bayo arrived, he certainly had a point. After all, Celtic have spent the last couple of months with only one senior recognised striker in the side in Edouard and had few options when their record signing was unable to play.

READ MORE: Brendan Rodgers: Celtic won't make any expensive marquee signings during this window

While adding more forwards to Rodgers’ squad has been the priority at Celtic Park this month, the club have acted swiftly and now the Celtic manager must look at other areas of his side to improve. And there’s one area in particular that has been overlooked for years and is in desperate need of an upgrade.

Right-back has been a problem position for a number of years at Celtic now and yet very little has been done to remedy this. Mikael Lustig’s best days are well and truly behind him but the curious thing about the whole situation is that Rodgers almost certainly feels the same way, and has done since he took over the club in the summer of 2016. Why, otherwise, did Rodgers bring in Christian Gamboa during his first transfer window at the club?

The Costa Rican has never really got going at Parkhead and has failed to make much of an impression during his two-and-a-half years in Glasgow. Some of the blame lies with the scouting department here, but Rodgers must accept responsibility for refusing to acknowledge the issue since. A player was signed and didn’t work out and rather than identifying someone else to come in, Rodgers has relied upon an aging Lustig and focussed on upgrading other areas of the team.

Over the last four seasons, Lustig’s ability has been on the decline as age has caught up with the 32-year old. Since the 2015/16 season, the Swede has contested fewer defensive duels year-on-year, made fewer interceptions and has started giving the ball away to the opposition more. His tackling success rate did improve under Rodgers compared to his time under Ronny Deila but this has dropped off significantly this season too. He’s attempting more headers, to Lustig’s credit, but doing so less successfully.

The numbers don’t tell the full story, however. Celtic fans will be all too aware of Lustig’s tendency to go missing in a game if he gets off to a poor start. If a winger can beat him once or twice during a game’s opening exchanges, Lustig’s confidence evaporates and he becomes a glaring weak point in Rodgers’ side. Last month’s Old Firm is a perfect example of this: Rangers’ Ryan Kent drove at him confidently and Lustig couldn’t deal with it. The right-back refused to commit to tackles in case Kent skipped past him, and was ultimately at fault for the only goal of the game because of this.

READ MORE: What can Celtic fans expect from Vakoun Issouf Bayo?

This isn’t revelatory for anyone who’s watched Celtic in Europe over the last few seasons. This is now Rodgers’ sixth transfer window at the club and after identifying this weakness in his first few weeks in charge, the former Liverpool manager tried to fix it by bringing in Gamboa. That didn’t work out, and yet the Celtic boss has done nothing since. Anthony Ralston is a decent option at a domestic level but has failed to impress in European competition. In short, Celtic don’t have a right-back capable of producing an effective display in the biggest games and haven’t for years.

Bringing in expensive players like Edouard or Olivier Ntcham will always excite fans, given the nature of their role in the team. But the most effective way of improving a side is undoubtedly by replacing its weakest player. Football is a game of fine margins and exploiting any perceived weakness in the opposition is the most practical way of winning a match. Bringing in an exciting forward or a dominant midfielder placates fans but it doesn’t make as big an impact as replacing your worst player.

The transfer window still has a few weeks to run and Celtic still have plenty of time to bring in another full-back. The fact that the club continue to be linked with right-sided defenders bodes well for Celtic fans and hopefully means that there is some progress being made on this front. Bringing in the likes of Weah is all well and good but the truth is that it is time that Celtic finally sorted out their problem at right-back. It’s a situation that has been dragging on for years and one that the club are clearly aware of, yet have done very little about. Bringing in someone like Elabdellaoui might not be the sexiest signing Celtic could make, but it might just be the most important transfer the club have made in years.