Mazzarri was pleased with the manner of their victory.
"This term the Champions League took a lot of energy out of us, but now we've got to focus and continue to improve," said the Coach.
"Up until we went 2-0 up there were risks of an equaliser. We have got to be more concentrated in defence. The second half performance was excellent and now let's keep going.
"I worry that we can get a little complacent and we should've played earlier the way we did when 3-0 up.
"For the past two seasons we have done extraordinary things. We've got to carry on along this path. This team has grown so much in just two years."