Speaking in an exclusive interview with ESPN FC, the BT Sport pundit said: "The mentality has got to improve".
It leaves Chelsea needing a new midfielder as well as reinforcements at wing back in the final days of the transfer window.
"He hasn't proven himself in the Premier League", "He has never started consistently in his career", "He had a poor preseason" - these are just some of the comments I have heard from friends who follow Chelsea and pundits who know a lot about the game.
"Every game becomes tough".
'Any silverware is important, even the so-called lesser trophies like the League Cup, because it sets a winning mindset but the league is the title everyone wants'.
Frank Lampard spoke exclusively to ESPN FC.
The opening game of the season comes at a bad time for Chelsea considering that the Premier League champions have yet to properly reinforce the squad. That means they will have to win the league again and have a strong run in the Champions League.
Nemanja Matic is a "great loss" for Chelsea says Antonio Conte
But Mourinho was nevertheless impressed with his former Chelsea charge: "I think he played really well, I think in the moment they were moving the ball well of course was hard for us in the midfield". "He's going to strengthen Manchester United ".
Premier League 2017/2018 begins: Top 5 things to look out for
The Gunners got the 2017-18 season underway with a thrilling encounter with Leicester City at the Emirates Stadium on Friday. The Gunners have been linked with a move to sign the France worldwide regularly over the past two or three seasons.
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"The investment of all the top teams is changing the landscape and it's not just that - the quality of the league as a whole has improved".
Wenger cleverly set his own team up in the 3-4-3 formation against Chelsea, thus crowding the middle of the park, to make it hard for the Blues to play their swift attacking game.
Conte has also penned a new Chelsea contract that did not extend his term at Stamford Bridge and he was evidently tired in the face of questions regarding further new singings after last weekend's penalty shoot-out defeat to Arsenal in the Community Shield.
Meanwhile, Liverpool playmaker Philippe Coutinho and Arsenal forward Alexis Sanchez are the subject of interest from Barcelona and Paris Saint-Germain, respectively, but their clubs say they will not be sold.
Chelsea managed an incredible thirty wins during their title win in Antonio Conte's debut season including a 3-0 home victory over tomorrow's opposition.
"I thought the referee was really good". Me, I have to start to study a new formation with ten or nine players. Dyche has looked for proven Premier League players and will hope that they have the tools to help the Clarets, as they could face another year of battling in the bottom half of the table. "But you know very well that there are surprises".
"I think I have for sure a good relationship with the club, with my owner", he said.
"My only task is to be focused on the pitch and work with my players".