Mourinho's side are currently four points clear at the top of the Premier League, but after letting leads slip against both Manchester City and United, their killer instinct has been called into question.
"If a team are going to be playing for a 1-0 then you better see it out," Neville said on Monday Night Football. "When I saw Jose Mourinho two weeks ago he talked about the 2005 (Chelsea) team and (compared) the team he had then to the team he has now and he said the killer instinct's missing.
"When I look at the statistics they are staggering - 28 times they (the 2004/05 team) scored first (in Premier League matches), 27 the season after and they only dropped two and four points (respectively).
"This team this season, even though they're at a really high level, have scored first seven times and already dropped four points. They've got to get to that next level."
For the big stories and the banter follow us on Twitter: @tribalfootball