Chelsea exited the Champions League with a semi-final second leg loss at Atletico Madrid and play Norwich on Sunday and Cardiff on the final day of the Premier League season with their title hopes relying on both Manchester City and Liverpool slipping up.
Mourinho draws a distinction between the recent losses against Aston Villa and Sunderland - where his thoughts on the officiating were made clear to the extent that he has been subjected to Football Association disciplinary action - with the defeat at Crystal Palace, where he believes his players lacked "balls".
The Blues boss has been impressed with the development of many of his players - Willian, in particular, although the Brazilian could score more according to his manager - but even Eden Hazard has been left in no doubt he has work to do after his midweek lapse against Atletico.
"You can't improve John Terry, Ashley Cole and these guys. If you keep them in the position where they are, it's fantastic," Mourinho said.
"All of the others have to improve. You can't succeed with everybody.
"You try to help, but it's up to them. Every one who is in an age of improvement needs to improve.
"For example, has (Andre) Schurrle had a good season? Not bad, but next season must be better. Much better, I think.
"Schurrle, (Mohamed) Salah, Oscar, Willian, Hazard... all of them are in an age of improvement."
Oscar was Chelsea's leading performer in the early part of the campaign, but the Brazil playmaker will miss the Norwich contest with a hip injury.
"Oscar was our best player for months, from August to November, December," Mourinho added.
"He was absolutely fantastic. And after that, he was (going down), no doubt.
"The reasons why, I don't think I should (explain), because some of them are from the personal side of the man, not the player."
Niggling injuries have contributed to Oscar's performance dip, but Mourinho expects the Brazilian, who played from the London 2012 Olympics through to the 2013 Confederations Cup without much of a break, to rise again.
"He arrived in the crucial moment of the season in a down," Mourinho added.
"I can imagine, in a couple of weeks, he will be in a high and during the World Cup he will be in a high."
Mourinho lauded his first-choice defence of the campaign - Branislav Ivanovic, Gary Cahill, Terry and Cesar Azpilicueta - and believes the midfield was disrupted by the fact January recruit Nemanja Matic was ineligible in the Champions League and Ramires was hit with suspensions, the latest of which means he is out for the final two games of this season and the first of next term.
"Ramires is a player that was suspended for eight matches in the Premier League, a gift of four plus a gift of three plus an accumulation of five yellow cards," Mourinho added.
"Between (Frank) Lampard, age, he doesn't play every game, Ramires and the suspensions, Matic not playing in one competition... it was an area where it was difficult to establish real stability and foundation."
There has been much focus and scrutiny on Chelsea's strike-force, with Mourinho lamenting the lack of goals.
Chelsea have made no secret of their desire to recruit a striker this summer, with Atletico's Diego Costa hotly tipped to be joining the Blues, and Mourinho believes that could make a significant difference.
"If next season we have a number nine who we decide is first choice, plus the stability that Matic can give by being always available, by Ramires who hopefully gets like the other players (one match ban after five yellows and nothing more than that), hopefully we will have more stability," Mourinho said.
He insisted, though, that his current crop of strikers - Fernando Torres, Samuel Eto'o and Demba Ba - had done well.
"The strikers I was trying to go from moment to moment, from quality to quality, trying to choose this player for this game, and I think we were successful in that," Mourinho said.
"Eto'o against Galatasaray, he scored. Torres in Istanbul, he scored. Ba at Liverpool, he scored.
"Against Atletico, we decided to play with Fernando and he scored.
"The other three positions were where it was easy to change between Hazard and Schurrle and Salah and Oscar.
"The structure, the base, is there partially and it was not possible to complete that puzzle for different factors."