The Championship side confirmed the 58-year-old's departure little more than two hours after the fifth round tie which saw Thistle take a shock first-half lead before eventually succumbing to a 3-2 defeat.
The Jags were widely praised for their performance – making the timing of the announcement somewhat peculiar – but they had previously lost back-to-back home league games to Cove Rangers and Hamilton Accies. McCall has now departed the club along with the rest of his backroom staff leaving the Jags sitting fifth in the Championship, 10 points behind leaders Queen’s Park.
A club statement read: "Partick Thistle FC have this evening relieved Ian McCall, Alan Archibald and Neil Scally, of their duties in relation to the first team with immediate effect.
"The club would like to place on record its sincere appreciation to all three for their contributions to Partick Thistle over many years.
"Under 18 coach Kris Doolan will take on the role of First Team Manager on an interim basis, and will be assisted in this regard by Academy Director Paul McDonald.
"At this crucial juncture of the season, we ask all members of the Partick Thistle family, to get behind Kris and the team as we strive for promotion to the Scottish Premiership.
"No further comment will be made this evening."