He said: "It was hard - physically probably our hardest game. In the last half hour, I don't know how many balls they put into our box.
"I can't criticise them for effort. We ran out of legs and we have got to address it, although that's difficult to address when there are sometimes two games a week.
"If we are not good enough then that's a problem - if we are not fit enough then we have got to do something about it. We all agree we are moving in the right direction because they are improving with each game."
Kevin Phillips once again failed to score for the Black Cats, but Wilkinson told Sky Sports: "We got 10 more minutes out of Kevin than we did at Bolton which is an improvement.
"He's had a very 'in and out' last five or six months. He has got the talent so fitness, in a sense, is the easy bit."
CHARLTON MATCH REPORT
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