It's crunch time in the January transfer window. Now, Mikel Arteta must lock in his final decisions of which Arsenal pieces to move across the board.

The window officially closes on Monday, February 3 and - as of right now - Arsenal are yet to conduct any business. This is despite persistent conversation around the striker position and amid a rapidly unfolding set of circumstances at full-back.

Arteta had started the season with Riccardo Calafiori on the left-hand side of defence though, three times already, has lost him to injury. He returned to net the winner at Wolves last weekend.

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In that match, Myles Lewis-Skelly was controversially sent off for serious foul play. It put the 18-year-old on course to miss their next three matches against Manchester City in the Premier League, the League Cup semi-final second leg away to Newcastle United and then the following top-flight meeting with Leicester City.

Kieran Tierney would be required to step up, in either's absence. The peculiarity of that situation is that his spell at Arsenal is, seemingly, coming towards their end.

Into the final six months of his contract at the Emirates Stadium, football.london understands the 27-year-old has been in discussions with Celtic over a return for some time.

With the window open for only a matter of days it has remained unclear if this would happen this month or in July, with the Scottish giants also now having their say.

"Ideally, that would [happen in January] but, at this moment, he's still an Arsenal player," Celtic's manager, Brendan Rodgers, said during his pre-match press conference before a Champions League game with Aston Villa.

Confirming there is a pre-contract agreement, at least, in place, Rodgers added: "I think everyone is agreed that it will definitely take place in the summer. If we can do it beforehand, then great."

If Calafiori can remain fit, that is one factor which could hasten Tierney's return to Scotland. The other is the appeal of Lewis-Skelly's red card and suspension, which has now officially been confirmed by the FA.

The 18-year-old can now face City, Newcastle and Leicester, therefore alleviating pressure on Tierney and perhaps clearing the path for a late-January deal with Celtic.

The only player unaccounted for inn that role, therefore, is Oleksandr Zinchecko. The Ukrainian is also closer to the exit door than his arrival to the club with interest lingering from European teams.

His potential exit could well be the final deciding factor in whether Tierney is allowed to fulfil Rodgers' wishes this January, or whether all parties involved might have to wait until the summer window.