Chelsea were 2-0 up and coasting until Leicester's Steve Guppy and substitute Ian Marshall began taking their defence apart in the last 20 minutes. The visitors scored two late goals to prevent Chelsea moving within a single point of Manchester United at the top of the Premiership.
Vialli defended the decision to send on Michael Duberry for Albert Ferrer in order to combat Marshall's aerial strength, but said he would have changed at that stage to a back four instead of persisting with three centre-backs, plus wing-backs. The system had been changed from 4-4-2 for the first time since the game at Derby in December, when a late equaliser also cost two points.
"I made a mistake which I take full responsibility for, because it's our responsibility to pick the right players and make the right substitutions," he said. "In 10 minutes we almost threw away what we've done for 10 months, but it happens in football."
Vialli agreed that the title now lies between United and Arsenal, who moved back in front of his team by thrashing Wimbledon 5-1 on Monday. "We have to learn from Manchester United to put the ball in the back of the net as often as possible, and from Arsenal in the way we defend and from their consistency and great spirit," he said. "It's now in their hands. We are third and will try to win the next five games but I don't think it's going to be enough. We hope we're going to have a positive reaction. You might be disappointed but you have to look at the next match."
That next game is the European Cup-Winners' Cup semi-final, second leg away to Real Mallorca tomorrow, which Chelsea must win. After being held 1-1 at Stamford Bridge they are optimistic that their goalkeeper, Ed De Goey, will be able to play despite a broken toe on his kicking foot, sustained towards the end of Sunday's match.
De Goey has played in more games than any other Chelsea player this season - 46 out of 50. He missed the first leg of the first-round European tie against Helsingborgs, when Dmitri Kharine made one of his four appearances. Kharine and Kevin Hitchcock will both travel to Spain today as cover, but there are no other injury problems.