Manchester United's first-leg victory over Granada a week ago was almost perfect.
A beautiful strike from Marcus Rashford and a dubious penalty from Bruno Fernandes secured a 2-0 victory in the first match of their Europa League quarter-final tie, giving Ole Gunnar Solskjaer's side the perfect springboard to qualify for the final four of this season's competition.
The reason United's win in the south of Spain fell just short of perfect was down to one thing, their discipline.
Solskjaer sounded genuinely disappointed when he dissected the match, ruing the fact Harry Maguire, Luke Shaw and Scott McTominay will miss the second-leg at Old Trafford this week after they all received one-match bans for an accumulation of yellow cards in the first-leg.
Yet despite a comfortable lead there would have been little surprise to see the trio start again this week, such is Solskjaer's trust in them compared with others in his squad.
However, on Thursday night he has no choice but to be experimental - in defence he has a simple decision to make.
Alex Telles will be a straightforward selection at left-back given his run of games in Europe already this season, but at centre-back all eyes should be on Axel Tuanzebe, who simply has to be given a chance to play.
In what was supposed to be a defining season for Tuanzebe he has instead stagnated, with a minimal role to play in the first-team.
One quirk is that he has played more minutes in the Champions League than the Premier League this campaign, but still only 554 minutes across all competitions in total.
Maguire's absence against Paris-Saint Germain back in October provided Tuanzebe the platform to showcase his talents in a sensational coming-of-age-display against Kylian Mbappe, however the hype has gradually dwindled after errors in subsequent appearances against Istanbul Basaksehir, Sheffield United and Everton.
That brief cameo against Everton at the beginning of February, where he needlessly conceded a 95th-minute free-kick from which United conceded deep in injury time, was his last league appearance in a United shirt.
A second-half introduction followed in the previous Europa League second-leg dead-rubber against Real Sociedad, where Tuanzebe should have netted his first United goal, if not for a foul by this week's probable defensive partner Victor Lindelof seconds before the ball flew into the back of the net.
In his debut season under Solskjaer the youngster captained the side against boyhood club Rochdale in the EFL Cup and was earmarked for a regular role in the line-up, but injury and inconsistency has ultimately been his undoing at the club.
With United set to pursue a new centre-back in the summer, coupled with the emergence of both Teden Mengi and Di'Shon Bernard in loans at EFL clubs, it seems time is gradually running out for a player so highly rated in his upbringing.
Just as Jesse Lingard has rejuvenated his career with a loan move to West Ham it could soon be an opportunity for Tuanzebe to pursue a similar pathway in the summer. A return to former club Aston Villa, or a spell at Newcastle, are options which would surely be welcomed by all parties, with Premier League interest likely high in a player of his pedigree.
Even if that is to be the case United would be foolish not to make the most of him while he is still at the club, the second leg against Granada could be his final chance to prove he is up to the demands at such an elite level.
A standout display could be the lifeline he needs to turn his Old Trafford fortunes around, while an underwhelming performance could reaffirm the doubts which have began to creep in this season.
Either way, we won't know until he is given a fair chance to showcase his talents. Not playing him against Granada would be inexcusable.