The Scottish Premiership side meet Rangers at Hampden Park on Sunday.
Although the Norwegian could still win a second consecutive double, he has come under extreme pressure at times this season.
And ahead of their Old Firm clash at Hampden Park, MacLeod predicted that defeat to the Scottish Championship side would spell the end of Deila's tenure at Parkhead.
He told The Scottish Sun: "If he doesn't win then I think he's under pressure. Would you sack a man that wins a league and cup double?
"For me that's very difficult - but if he loses this game I think it would be the final straw.
"The title is just not enough this year. You've got a semi-final against Rangers.
"If it was someone else there would still be a bit of pressure.
"But I don't think there's any way that if Rangers win, he's surviving until the end of the season."
While the Hoops hierarchy will probably be keen to avoid any rash decisions in the event of a surprise defeat to Mark Warburton's men - if they are considering the manager's future at all - the fact that they would not only be losing to their bitter rivals, but would also be unable to match their trophy haul of last term would make it very difficult for the Bhoys to justify keeping him at the club.
Deila may have handed opportunities to several younger players this season, but the team start the campaign in enough competitions for there to be enough chances for the prospects to come in without it having a major impact on their form.
And with it being Rangers that would be ending Celtic's chances of winning the double, the calls for him to go may reach a level that the club's board become unwilling to ignore.