In the summer, Arsenal made it clear that Manchester United could only sign Thomas Vermaelen if they offered Chris Smalling in exchange. But Louis van Gaal, keen to give all his players a fair crack of the whip, rejected the offer. By half-time of Sunday's Manchester derby, however, the Dutch coach must have wished he'd agreed to the deal.
The 24-year-old centre-back embarrassed his manager by picking up two of the most foolish bookings you're ever likely to see - particularly in such an important match.
Smalling earned his first booking by standing in the way of Manchester City goalkeeper Joe Hart, who was trying to clear the ball, before stupidly diving in on James Milner minutes later.
It proved to be the game's turning point. Before Smalling's two moments of pure stupidity, Manchester United were looking reasonably comfortable considering they were playing at the home of the reigning champions.
The Red Devils went on to lose the match 1-0, after their resistance was finally broken by Sergio Aguero, leaving Manchester United fans - and Van Gaal - furious with Smalling's incompetence.
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The England international will be suspended for next weekend's Premier League clash against Crystal Palace, but it could be a little while longer before the incensed Van Gaal selects him in his starting line-up again.
Barring his display against Chelsea last month, Smalling has failed to impress this season - and, like most of his defensive teammates, has struggled with injuries.
Van Gaal has doubts over Smalling
It was revealed several weeks ago that Van Gaal has doubts over all three of his first-choice centre-backs - Smalling, Phil Jones and Jonny Evans - and will look to rectify the situation when the transfer window re-opens in January.
Of the three defenders, Smalling is surely the one most at risk of being axed. Physically strong and measuring in at 6ft 4in tall, the former Fulham starlet is certainly a tremendous athlete - but does he possess the required mentality to become a top-level defender?
Concentration is key - and doubts over Smalling's ability to remain focused will have increased following Sunday's shambolic performance.
Back in February 2011, Ferguson proclaimed that Smalling and Evans would be Manchester United's first-choice centre-back partnership for years to come. But both defenders, Smalling in particular, have flattered to deceive for too long now.
Van Gaal may consider selling Smalling
Van Gaal will be acutely aware that failure to rectify United's defensive issues in the New Year cost ultimately cost him his job. While there have been signs of improvement - and a clear plan in place - under the former Bayern Munich and Barcelona boss, the fact is United have won just three of their first 10 matches and currently sit tenth in the Premier League table.
That's an even worse record than David Moyes' first few months in charge at Old Trafford, and Van Gaal is still in the process of convincing supporters - and the club's hierarchy - that he's the right man for the job.
The 63-year-old has already shifted much of the deadwood at Old Trafford, but part two of his clear-out will involve Smalling unless he proves over the coming weeks that he deserves to remain a Manchester United player.