Former Celtic boss Ronny Deila believes Virgil van Dijk won his move to Liverpool after changing his attitude towards fitness training.

The Dutchman played under the Norwegian at Celtic Park for a year, winning the Scottish Premiership in 2014/15.

"I think he was not fit enough to be at the highest level," Deila told theA Celtic State of Mind podcast when referring to Van Dijk's early days at Celtic.

"He has unbelievable skills and potential but he needed to be better to train everyday, take care of himself better and I think he progressed a lot in that year to be more conscious about how he lives his life after football and also how he trains.

"He was so good after this period."