Maurizio Sarri lauded Chelsea's spirit after they stole a 1-0 win at Slavia Prague despite a poor performance on Thursday.
The Blues lead their Europa League quarter-final tie after the first leg thanks to Marcos Alonso's late header, but they were outplayed for long periods away from home.
Sarri said he had always expected a stern test against Slavia but was pleased to see Chelsea show their character by staying in the game and then getting a potentially pivotal away goal.
"I think we knew very well that it would be really very difficult," he told a post-match news conference.
"The opponents are very physical, very aggressive and so we knew we had to face difficulties during the match. We were able to front up and face them well and then, in the second half, we were able to play better.
"We need to think the second leg will be difficult, too, because these opponents are dangerous away - like in the round against Genk. We need to be careful.
"I am happy with the result and also the performance because, in this moment, we were able to suffer [and come through]. In the past, we weren't able to suffer in difficult moments.
"This is not for the first time but in the past, when we were in trouble, we conceded immediately. Now we can fight and suffer without conceding. That's a step forward."
Eden Hazard started on the bench, while Callum Hudson-Odoi was left out completely, with Sarri suggesting the teenager needed a rest.
On Hazard, the coach said: "I wanted him on the bench because I thought this match would be difficult and I would probably need to use him. If we were 1-0 [up] at half-time, I wouldn't have used him."
Sarri was also asked about video footage that appeared to show Chelsea fans aiming racist abuse at former player Mohamed Salah.
The club condemned the alleged incident and promised to take action, but Sarri had not seen the video as he addressed the media post-match.
"I don't want to talk about this because I didn't see the video, so I don't want to talk about something I don't know about the case," he said. "I want to speak about football.
"I think [the club statement] is right. I don't want to speak about something I don't know. It's not right if I talk about something I don't know. It's right that the club has a strong response."