Luke Shaw
Luke Shaw's injury left United with a problem at left-backGetty

Manchester United host PSV Eindhoven in their penultimate Champions League group stage tie tonight (25 November) in a match that should see them secure their place in the knock out stages. But it will also serve as a reminder of the night in September when Luke Shaw suffered a horrific double leg-break in the reverse fixture, one that effectively ended the 20-year-old's campaign.

After an extensive pre-season training schedule, which he began before any of his teammates, Shaw began the 2015-16 campaign as arguably his side's best player, an impressive feat given where he plays. Louis van Gaal recently told reporters the defender would currently be regarded as the "revelation of the season" had injury not struck him down. It's difficult to argue with that sentiment.

United conceded just three goals in their opening seven games before losing Shaw. While Van Gaal's pragmatic approach has ensured his side retain the best defensive record in the Premier League, the left-back's absence has been felt.

During the first three months of his recovery, Daley Blind, Marcos Rojo, Matteo Darmian and Ashley Young have all deputised. Shaw's injury struggles last season allowed Blind to make the left-back slot his own for much of the second half of the campaign, including the period where United hit a sublime run of form in March and April that saw them record wins over Tottenham Hotspur, Liverpool and Manchester City.

As he has demonstrated at centre-half this season, Blind is intelligent enough to fill in anywhere across the backline, while his vision and range of passing allowing him to make a telling contribution going forward. But since Shaw's injury, he has featured at left-back just once in what is a testament to his ability inside along Chris Smalling, rather than any lack of faith from the manager in his qualities at left-back.

Marcos Rojo
Marcos Rojo has shown plenty of good but some bad since stepping in for ShawGetty

Rojo has been the closest thing to a direct replacement for Shaw. The 25-year-old occupies that role for Argentina and, based on his time in Manchester, seems to be more suited to that role than centre-half. Encouragingly, Rojo has shown he is an adept deputy in the majority of his 13 appearances there.

In September and October he turned in strong performances against Manchester City, Wolfsburg and Everton, the latter seeing him provide an excellent cross for Ander Herrera's opening goal at Goodison Park. In those games, the rash decisions and poor positioning that have often been cited by his critics saw a significant improvement. That development was marked again in the 2-0 win over West Bromwich Albion on 7 November, where signs that he is finding a better balance between aggression and composure were clearly evident.

Among those matches, however, was a particularly nervous performance away to CSKA Moscow on 21 October, where Rojo appeared terrified of the prospect of crossing the half-way line. That was pounced upon by CSKA boss Leonid Slutsky who ordered Brazilian fullback Mario Fenandes to attack the Argentine at every given opportunity. Rojo didn't cope well, and was taken off with half an hour to go.

He was also guilty of giving away a rash penalty against Watford at Vicarage Road on 21 November, an incident that could have cost his side three points. It was a surprise given the progress he had made in previous weeks, where his tenacious performances have helped soften the blow of Shaw's absence.

Matteo Darmian
Matteo Darmian has looked unconvincing at both right-back and left-back after his impressive start to life at UnitedGetty

Darmian, who also enjoyed an excellent start to the season at right-back, was moved across to the left to fill the void against Sunderland back on 23 October, where he was largely untroubled. Days later against Wolfsburg he retained the slot but was partially at fault when the Germans took the lead after just four minutes as he played Daniel Caligiuri onside –although Antonio Valencia's woeful positioning also contributed. The following weekend, he returned to right-back where his worrying decline after such an impressive start was brutally highlighted against Arsenal, as the Gunners cut United to ribbons inside 20 minutes. Darmian was taken off at half-time.

Ashley Young, often one of United's most creative forces in the second half of last season, has impressed in defensive roles this term, but injury to Antonio Valencia and Darmian's lack of form has seen him start on the right hand of defence three times, compared to just once on the left. 18-year-old Cameron Borthwick-Jackson was also handed the chance to impress at left back against West Brom. It was more than a throwaway gesture from Van Gaal, too. At the time of the teenager's introduction, United were still only 1-0 up.

Collectively, those stand-ins have done a steady job. United have conceded just eight goals in 13 games since losing Shaw, going over 600 minutes without letting one past them until Troy Deeney hammered a penalty past David De Gea at the weekend. But Shaw's absence is still clear, according to Van Gaal, who could use the January transfer window to bring in a player more to his liking.

"I was convinced Luke would have a very good season and because of that I didn't want to buy a second player for left-back," he told Sunday newspapers after the Watford victory. "Maybe we have to buy a left-back in January."