The Mexican came up with the winner in the 4-3 victory over Newcastle, making it ten for the season so far.
That puts him well on track to match the 20 he scored in his first season, doing much better than the twelve he hit last term.
Ferguson told reporters: "Every time Javier has played he has contributed.
"He has got 10 goals now and that is despite not playing every week.
"On Wednesday he could have scored four or five. Javier must have run about 20 miles against Newcastle - he never stopped."