Wigan's steady improvement since their 2005 promotion to the top flight is reflected in their results against the Reds - after 14 straight defeats (15 if you include the 2006 League Cup final), they finally beat United 1-0 in the last meeting.
That surprise win at the DW Stadium in April helped Roberto Martinez's side to comfortably retain their top-flight status - Wigan went on to finish three places and seven points above the drop zone - and also dealt a huge blow to United's title hopes.
"When you come to the end of the season and you drop points it has a big impact," Sir Alex said on Friday.
"I think it was Everton [4-4 at Old Trafford] which killed us. But you could easily say it was the Wigan game. I thought they played very well that night as they were fighting for their lives to avoid relegation. It was an understandable result in such a tight game."
The United boss admires his opposite number at the DW Stadium, and his loyalty to the Latics.
"There’s a consistency and continuity in the management at Wigan," said Sir Alex. "Roberto Martinez turned down opportunities to speak to two or three clubs over the last few years and they also have a great chairman in Dave Whelan.
"They could be a club on the rise in the next few years. I don’t think they’ll ever get massive crowds – it tends to be a rugby league town – but they’re doing well on the football pitch.
"They've changed to playing with three centre-backs and it’s proven useful for them. It suits them