A flop isn't always a flop from the word go. In fact, plenty can look like excellent signings in the first few weeks or even months of their spell at a club, before things quickly do downhill.
Here's a look back at eight United flops who actually started very brightly at Old Trafford...
United Career: 2009 - 2012
Intended as a relief striker and impact substitute, Michael Owen was very much filling his purpose after he first joined United as a free agent in the summer of 2009.
That included scoring his iconic winner against a newly threatening Manchester City in a 4-3 derby classic, as well as four goals in the Champions League group stage and the equaliser in the League Cup final United went on to win, all before the end of February.
But injury prematurely ended his 2009/10 season and also ruled him out as an effective squad option for most of the rest of his Old Trafford stint.
United Career: 2004 - 2007
Even though participation at the 2004 Olympics with Argentina delayed the start of his United career, Gabriel Heinze quickly became a fan favourite following his arrival from Paris Saint-Germain and became an automatic pick at left-back.
Heinze ended his debut season as Sir Matt Busby Player of the Year, only for serious injury to wreck his 2005/06 campaign. He returned to action the year but things weren’t quite the same and he ultimately dug his own grave when he tried to force a transfer to Liverpool.
United had no choice but to get rid, and sanctioned a move to Real Madrid instead.
United Career: 2004 - 2007
Alan Smith marked his home debut with a stunning goal against Norwich in August 2004, as well as an assist in a 2-1 win. He followed that up with another strike against Blackburn the next game.
Those early performances quelled any doubts given the relatively controversial nature of his summer transfer from a recently relegated Leeds, although the arrival of Wayne Rooney immediately made competition for places much tougher.
Despite injuries to Ruud van Nistelrooy and Louis Saha, Smith only scored once in the second half of the season. He then reinvented himself as a somewhat limited midfielder but a broken leg effectively marked the end of his time in Manchester.
United Career: 2004 - 2008
Injury stopped Louis Saha from fulfilling his potential at United, which was especially frustrating because he scored seven times in his first 12 Premier League appearances for the club.
That flurry followed his January 2004 switch from Fulham, yet the Frenchman could only manage seven league starts and one goal in his first full season. The 2005/06 campaign was better, but Saha never managed double figures in the league for United.
He took on a greater role in 2006/07, by which time Wayne Rooney and Cristiano Ronaldo had properly come to the fore. Carlos Tevez joined that group in 2007/08.
United Career: 2003 - 2007
Tim Howard is among the greatest American players of all time, and it was at United where he kicked off a lengthy Premier League career when he arrived from MLS in the summer of 2003.
Howard replaced World Cup and two-time Premier League winner Fabien Barthez as United’s starting goalkeeper and quickly showed he was a worthwhile gamble from Sir Alex Ferguson as he finished the 2003/04 season in the PFA Team of the Year.
Unfortunately, Howard failed in what was an ongoing quest from the club to replace Peter Schmeichel. He was relegated to second choice early in 2004/05 after a difficult start to the season and never recovered his position.
United Career: 1999 - 2000
The lasting memory of Massimo Taibi’s United career remains the weak Matt Le Tissier shot that squirmed under the Italian’s body in a 3-3 draw against Southampton. Yet a fortnight earlier the Italian had been Man of the Match on his debut against Liverpool.
Taibi joined from Venezia for a sizeable £4.5m in late summer 1999, with new number one Mark Bosnich already injured. He was guilty of a goal-costing mistake against Liverpool but made up for it with a number of important saves to contribute to a 3-2 win.
He never recovered from the Southampton howler and conceded five a week after that as United were thrashed by Chelsea in a first Premier League defeat in nearly 10 months.
United Career: 1996 - 2000
His family name understandably brought immense expectations, but Jordi Cruyff looked to be fulfilling them for at least a few weeks at the very start of his United career in 1996.
The versatile Dutchman had already enjoyed a positive start to his senior career at Barcelona, where he was actually the club’s joint top scorer in La Liga in 1994/95, and netted twice in his first three Premier League appearances for United.
Injury was a large part of the reason that was as good as it got for Cruyff. He missed most of the second half of that season and almost all of 1997/98. He did feature early in 1998/99 but spent the second half of the campaign on loan in Spain and was eventually released in 2000.
Angel Di Maria
United Career: 2014 - 2015
Excitement levels were enormous when Angel Di Maria completed a club record switch from Real Madrid in 2014, just months after a Man of the Match performance in the Champions League final and having also lit up that summer’s World Cup.
After a tentative opener at Burnley, the Argentine blew away QPR on his home debut and contributed nine combined goals and assists in his first 10 Premier League appearances.
Di Maria’s performances fell away thereafter, failing to adapt to Louis van Gaal’s tactics and management, while he struggled to settle off the pitch, especially after his home was the target of an attempted burglary midway through the season.
Source : 90min