Steve Cotterill took the blame for Portsmouth inability to beat Cardiff after they drew 1-1 at Fratton Park.
The Pompey chief believes that he worked his players too hard in training this week in preparation for the game.
Andrew Taylor gave the visitors the lead late in the second half only for veteran striker Kanu to spare his manager's blushes with a late equaliser.
"We gave a lethargic performance and I have to say it was my fault," he said.
"I trained them too much during the week so all the players are going to get my apologies.
"I have to take responsibility for that performance and for the fact that some of the players had left their legs on the training ground.
"I have to learn from this mistake but there is no doubt that we would have been a yard sharper on any other day.
"There was just not the zip that you would normally expect. Cardiff made two goal-line clearances and I think on another day if the players had not been so tired they might have got to the rebounds first."
Pompey twice hit the woodwork and had two other shots cleared off the Cardiff line.
Darcy Blake also hit the frame of the goal for the Bluebirds in the 15th minute before Joel Ward struck the Cardiff bar with an intended cross seven minutes later.
Greg Halford hammered a 25-yard free-kick against the outside of the Cardiff post after 48 minutes but then the Welsh club had two lucky escapes in the space of three minutes.
From the first of those Rob Earnshaw cleared a shot from Halford off the line and from the rebound goalkeeper David Marshall held the ball on the line at full stretch.
Then in the 66th minute Benjani Mwaruwari, making an emotional return to Portsmouth after more than three years elsewhere, saw his effort cleared from the line by Peter Whittingham.
Cardiff took the lead in the 71st minute when Andrew Taylor scored with a fierce left-footed shot after a sweeping move involving Earnshaw and Craig Conway.
Cotterill sent on veteran striker Nwankwo Kanu in the 75th minute in place of Luke Varney and the Nigerian scored the equaliser five minutes later.
Tal Ben Haim crossed from the left and Kanu headed in from 15 yards.
Cardiff manager Malky Mackay said: "I felt the draw was about right.
"Portsmouth will point to hitting the woodwork and having shots cleared off the line but we also had our chances.
"I felt that having gone ahead with not much longer left that we might have held on to win. We could have been a little more ruthless in those circumstances.
"We knew it would be a strong, physical battle. Portsmouth enjoyed their set-pieces but I think we acquitted ourselves well and got a good draw.
"I've looked at television replays of the shots cleared from the line and in neither case was there a goal."