The Scottish Premier League manager of the year has guided his side into the Europa League qualifiers for the second successive season after securing the runners-up slot behind Celtic.
Motherwell chief executive Leeann Dempster said: "I can confirm we had an approach from Sheffield United regarding Stuart McCall on Monday night."
McCall spent two years as a player at Bramall Lane before becoming assistant to Neil Warnock between 2004 and 2007, when the Blades were relegated from the Premier League on the final day.
His first job in management was with another former club, Bradford City, before replacing Craig Brown at Fir Park in December 2010.
Speaking after the 2-0 defeat at St Johnstone on Sunday, McCall said: "I think when you've had a decent season, or a couple of decent seasons which I've been fortunate to have, then speculation will grow.
"As far as I'm concerned, my full focus is on here all the time."
United are seeking a permanent successor to Danny Wilson, who departed in early April, with former player Chris Morgan taking temporary charge in the interim.