The Magpies right-back, who made eight appearances for Sir Alex Ferguson's side before departing in 2008, was magnificent on Saturday and played a huge part in frustrating the Reds during a frantic second half at Old Trafford, clearing a Javier Hernandez shot off the line in incredible fashion.
"It was just out of instinct," Simpson recalled to MUTV. "We had been watching tapes of Hernandez all week and have been watching his movement in the box. I saw the cross come in and managed to get back on the line, stick my foot out and I managed to clear it.
"I'm just glad we got a point because it was wave after wave of attacks in the last 15 minutes, but we managed to deal with it. We've been defending like that all season. It is something that we have been working on in training and it is nice when it pays off at a place like Old Trafford."