"We never give up," the Scot told MUTV. "Of course, it's in the history books. Well done to the lads for coming back. We do that all the time at our club and I expect 10 like that a season so that's one out of the way! It's unbelievable - it really is."
Ferguson insisted that Van Persie, who also missed a penalty during the match, will only improve during his time with the club.
"Robin has got four goals in two starts, which is a great statistic, and he'll get better," he added.
The win has lifted United up to fifth in the Premier League table.