Next week, Manchester United will play their first knockout Champions League game since David Moyes' time at the club.
Jose Mourinho has guided United through to the group stages and they have been awarded with an winnable tie against Sevilla in the next round. This competition is one of the remaining two possible routes United have for silverware this season, with them still competing for the FA Cup, but the odds are obviously against them being crowned champions of Europe.
United may well currently be the second best team in England, when you look at how Barcelona, Bayern Munich, PSG and Manchester City are running away with their respective league campaigns, it would take a brave person to suggest United are in with a shout in the Champions League.
Yet Mourinho has won the competition twice and on both occasions his team were nowhere near favourites. No one would have fancied Porto to win it in 2004, or Inter Milan in 2010, but Mourinho came out on top.
Last season, Mourinho sacrificed United's league position to prioritise the Europa League to ensure silverware and qualification to the Champions League. With City so far ahead this season, you would imagine Mourinho might try a similar tact this season and put all his eggs in the European basket.
But even the most optimistic United supporter can see a huge flaw with this plan. His defence is an accident waiting to happen.
Chris Smalling and Phil Jones have suffered plenty of criticism in recent weeks and United fans are wondering what Marcos Rojo or Victor Lindelof have to do to get a game.
Of the two defenders to start most games at the back, Smalling is the most vulnerable to losing his place in the team after proving to be a greater liability than an asset. There's not even the slightest glimmer of hope that Mourinho can beat Europe's best teams, relying on defensively solid tactics, with Smalling in the centre of defence.
That's not to say that Smalling isn't capable of brilliant performances, or even good spells at the back, because he is. But he cannot be relied upon when it matters. He's also not much use when playing the ball out from the back either. He either cautiously passes it sideways to the nearest defender, or launches it up the field to no one. Lindelof, by contrast, is a much better passer of the ball.
The Sweden international took to social media this week to claim that he can play in a number of positions, including right-back, but it's in the centre where he feels most comfortable. Like Smalling, he's had some difficult games since signing in the summer, but he's five years younger than Smalling and is getting used to a different league. Smalling has obviously played here all his life though and still looks to be getting to grips with it.
Lindelof likes to bring the ball out to midfield and could help support United on the break, with the speed of United's counter, or lack thereof, a real issue. Although he has so much learning to do, the only way he's going to get there is if he's given the opportunity to improve. Surely there is more value in that than persisting with someone whose flaws are well known and who has little chance of improving.
In the 3-1 victory over Arsenal at the Emirates, with the home side dominating possession and chances, Lindelof held his own. When the pressure was on, he stepped up to the plate.
Too often, Smalling has gone missing in the big games. Mourinho wasn't at the club when Smalling was outjumped by Vincent Kompany in the 2012 derby that essentially saw City win the league. He also likely didn't pay attention to the two ridiculous yellow cards Smalling picked up in the first half at the Etihad to cost his team the derby in 2014. He might have missed Smalling scoring an equalising own goal in the 2016 FA Cup semifinal before getting sent off in extra time for a rugby tackle that could well have seen United's 12 year run without winning the competition continue.
The fans obviously saw all of those moments though and the attrition of watching Smalling show his vulnerabilities has reached breaking point for many. Lindelof may have been written off by some a few games in but, after some better performances, even he seems like a safer bet than the combination Mourinho has kept choosing.
The idea of seeing Smalling tasked with keeping out the likes of Neymar, Lionel Messi, Robert Lewandowski, Edison Cavani and Luis Suarez is fairly terrifying. If he's not booting the ball in to the back of his own net, he's diving at the half-way line. If he's not injuring United's players, he's rugby tackling forwards he can't get close to. United's long absences from Champions League football has spared Smalling's blushes.
Eric Bailly is the defender all United supporters are desperate to see return in time for the Sevilla game, but they could do a lot worse than partnering him with Lindelof. Mourinho obviously wants to protect the younger defender and doesn't want to throw him in at the deep end. But with United's options of silverware running out, it might be a case of sink or swim for Lindelof, and he surely can't be any worse than Smalling has been.