Raheem Sterling put the visitors ahead but Romeo Lavia and Adam Armstrong responded as Southampton won 2-1.

"It is not enough to play 20-25 minutes on the level we want," said Tuchel.

Chelsea's other defeat also came away from home in a 3-0 humbling by Leeds at Elland Road last week.

"It is too easy to put us off balance, to beat us, to confuse us," Tuchel told Match of the Day. "It is too easy. It happened against Leeds. We need to understand why and find solutions.

"We lose concentration, we lose our plan and lose consistency, it is too easy to beat us.

"You can always lose football matches and I am humble enough to admit this but in a match where you are in the lead there is no need to give away half chances. To have no answers in the second half was disappointing.

"We need to have answers, we need to step up and play a level higher if needed. We struggled to do this."

Tuchel also bemoaned Chelsea's injuries, with defender Reece James missing out with illness.

He was also without N'Golo Kante, while Mateo Kovacic continued his return by coming off the bench in the second half when he replaced the injured Ruben Loftus-Cheek. Conor Gallagher was suspended.

"We started well in all the games almost but obviously we are struggling with our focus and consistency in matches," Tuchel added on BT Sport.

"We struggle to find answers and find the way back if things don't go in our direction.

"I don't know if concern is the right word. I absolutely dislike to lose, it is the second time this season and I don't think it takes a lot to beat us and this I don't like.

"We try to win matches and the way we do this is something we need to understand as fast as possible. I also don't understand why we are in this situation with injuries to all midfield."

Tuchel continued: "Soft, soft, soft defending. There is no need to give shots away. Just toughen up as a team and show a different mentality.

"I don't like to talk about it normally because you cannot prove it with the data, body position or with the tactical position in defeat. But it's like this.

"Both goals are cheap goals, soft goals, and should not happen if you expect to win a Premier League match, a night game and an away game.

"With our demands and the ambitions we have, it's even more important if key players are missing that we need to show a different mentality - it's too easy to push us off the track, it's too easy to win challenges, it's too easy to bully us."