Nemanja Vidic again struggled for Inter Milan in their 4-1 thrashing by Cagliari.
The former Manchester United captain gave away a penalty - saved by Samir Handanovic - for his mistimed tackle.
"He is probably one of those I used too much," said Inter coach Walter Mazzarri.
"He's strong and a leader, so I didn't want to rest him, but he was fatigued and therefore below par. I take responsibility for that, as I should've made more changes and realised there are players who at this moment cannot play three or four times in a row.
"Fatigue has an effect on your physical and psychological performance. Some players weren't sharp and all it takes is half a metre or your body leaning the wrong way when a player runs at you and there isn't the strength to make up for it.
"Mind you, some of the players who seemed stranded in the first half were woken up by those four slaps in the face."
