However, Ferguson admitted Arsenal started strongly in a first half which saw referee Phil Dowd have his own problems.
He said: "I thought the referee found it difficult and the game was running away from him, he found it difficult to control.
"Once we started getting some momentum going and a bit of heart, we looked like the team to win.
"We had some good headers in the first half, the goalkeeper has made a great save from one of them and Phil (Jones) has missed the other two.
"In the second half Wayne (Rooney) had a chance with a header and time and again the final ball let us down. We were the team making the chances. But credit to Arsenal, they kept fighting which is what we expected."
Ferguson also saluted Van Persie for staying cool as Arsenal fans tried to unsettle him with volleys of boos.
"He kept his nerve, that was important," said Ferguson. "It was a difficult time for him, the chanting from the fans does not help, but he kept his cool."
The Scot said there would be no let-up in his team's intensity even though the chance of a record Premier League total has now gone.
"We have got Chelsea next week," said Ferguson. "They are fighting for a Champions League place and we have to honour the rest of the teams who are trying to get there, like we did today.
"Nobody could say we relaxed too much, I thought we had the edge to the game in the second half."