But the Newcastle boss was quick to praise the part played by the Brazilian international in the draw with Middlesbrough.
In the 79th minute the 31-year-the old defender made a crucial sliding challenge to deny substitute Dong Gook-Lee after Shay Given had beaten out a shot.
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Had Cacapa not made his timely intervention, then Keegan might have lost his record of never having being beaten in a league derby fixture as United manager.
Keegan: "The best tackle of the game was Claudio's - it was a goal.
"It's worth a goal to us - there's no doubt about it.
"He was second favourite for a long while, but he wanted to win it."