Celtic manager Ronny Deila has praised Dundee United for maintaining their standards despite bringing in more than £5million in transfer fees this summer.

United sold Andy Robertson and Ryan Gauld in the close season but they remain firmly in the hunt for a European place and are still in both cup competitions.

And Deila is anticipating a much tougher encounter at Tannadice on Sunday than United provided in a 6-1 defeat at Parkhead in August.

The Norwegian said: "They have improved and have had a very good season so far. They have a lot of points and played many good matches.

"I like the way they play football. They defend hard with a very good team spirit and are very direct, very good in counter-attacks and also score a lot of goals from set-pieces.

"They are a very good team and have brought on a lot of young players.

"They also sold players for good money and still keep the team up. That's the sign of a good culture and a good club.

"It's going to be a very tough game but that's good, that's the games we need."

Celtic have won eight Scottish Premiership matches in succession since their home defeat against Hamilton but Deila believes there is plenty of room for improvement.

"We have been up and down but it's going in the right way," he said. "I think we have improved as a team and individually a lot of the players have been better and better. If we continue doing that, we will get better performances and results."