David Moyes was proud of his players following the 1-0 victory over AEK Athens but voiced concern over injuries to Dan Gosling and Sylvain Distin.
Everton booked their place in the last 32 of the Europa League after holding on to an early lead given to them by Diniyar Bilyaletdinov.
They had to battle the weather as well as their opponents, with torrential rain in the Greek capital making the pitch extremely difficult to play on.
Moyes said: "I was pleased, especially with the outcome of the game. The early goal helped us.
"The young players who came in did really well tonight and I'm delighted with them.
"It's very important to have qualified with a game to spare as it gives us a week where we don't need to be too intense with the squad.
"I think the conditions did play a part. It was an energy-sapping pitch.
"It was like back to the old days. I would have enjoyed it in my playing days but I don't know how some of the players felt about the conditions out there."
Everton have been plagued by injuries all season and Moyes was forced to make three substitutions against AEK.
Brazilian striker Jo came off in the second half, while Gosling and Distin were both replaced before the interval and Moyes is anxious to discover the extent of their problems.
"I don't think Jo's injury is serious," he said. "I am concerned about Distin and Dan as both are both hamstring strains. We will have them assessed tomorrow.
"I think the main reason for the injuries is down to overloading them. Sylvain has had to play just about every minute of every game."
Moyes hopes the victory will instil confidence in his players as they look to climb away from the lower reaches of the Premier League.
"Tonight was a case of needs must and I think the spirit of Everton was apparent among both the younger and more experienced players," he said.
"Tony Hibbert, again playing out of position at centre-back, did a great job.
"They all worked so hard to get the result, it shows there is a heartbeat at the football club and hopefully we can kick on from here and improve."