The Portuguese was already under intense scrutiny following a tumultuous summer and a surprising defeat to Brighton so this result will only make the situation worse.
Goals from Harry Kane and a Lucas Moura double meant Monday's 3-0 defeat at Old Trafford was Mourinho's biggest ever home defeat in all competitions as a manager.
The last time Manchester United lost two of their opening three Premier League games - back in 1992-93 - the club did actually go on to finish top of the table but the bookmakers can't see such a turnaround this time.
bet365’s Steve Freeth said “Manchester United did actually win the title the last time they had this sort of start, but playing catch up to the likes of Manchester City and Liverpool is likely to prove a lot harder than it was Aston Villa and Norwich City back then.”
The same firm now make United 50/1 (51.0) for the title, although given their performances the more important quotes come from markets regarding them missing out on key milestones.
It's now 2/5 (1.40) that the Red Devils finish outside the top four and 11/4 (3.75) that they finish outside the top six in the current campaign. While the performances will be a huge concern to the club hierarchy, missing out on the Champions League and its lucrative revenue stream would be a huge blow financially.
bet365 also have a market on when United will next win the title, going 1/8 (1.12) that they don't achieve the feat by the end of the 2020-21 campaign. They're 8/1 (9.0) to record a victory next season and 12/1 (13.0) to emerge triumphant in the 2019-20 edition.
In their final match before the international break, United travel to Burnley where they’re 8/13 (1.62) to pick up maximum points against a Clarets side that have also made a disappointing start to the season.
As a result of their 3-0 win on Monday night Tottenham are now 12/1 (13.0) to win the Premier League but still trail Manchester City (4/6) and Liverpool (5/2) who have also started with three consecutive wins. Chelsea are also 12/1 (13.0) to finish top of the table having taken maximum points from their matches to date.