Former Man City defender Danny Mills has identified Tottenham's problem area following their 3-1 defeat at Sheffield United on Thursday night.
Spurs saw their slim hopes of making the Premier League top four given another blow thanks to the shock loss at Bramall Lane.
The Blades had struggled since the restart while Tottenham came into the game having drawn with Manchester United and beaten West Ham.
But Mourinho's men were second best throughout as Sander Berge opened the scoring in the first half for the hosts, before Lys Mousset and Oli McBurnie added goals in the second period.
Harry Kane had a goal ruled out during the contest but added a consolation in the 90th minute to complete a disappointing evening for the Londoners.
Spurs dominated possession during the contest with a 64% share of the ball but couldn't break down the opposition. This has led to criticism of the club's attacking options but Mills, who was speaking on Sky Sports' Football Show, insists the problem area is just behind that.
"Harry Kane has been out for a long time. He is a quality player but Jose has not really had the chance to work with him a great deal," Mills told Sky Sports.
"It's a magnificent front three with pace on both flanks. He has played that system several times before with one dominant nine and quick players either side.
"The problem area, however, is perhaps who he should play in behind them in that number ten role."
But Mills doesn't just see midfield issues at Spurs, with the former England defender explaining that Mourinho will be looking for additions at the back this summer.
"A lot of top sides will be looking for defenders and it's the same at Tottenham," Mills added.
"When it was all about defence, we had some top-class ones across the world. It's not the same now. Mourinho is going to have to go out there and find someone to play alongside Davinson Sanchez.
"Mourinho is working the situation and is trying to defend his players. I think he will be going to the chairman and saying that they need more players to push on.
"Mourinho is not daft. He is a magnificent manager and should be asking for more and it will cost them money."
