Where do you get that Shaw is one of our fastest players ever? Fast as Giggs, Ronaldo, Valencia, James, Rashford, Kanschelskis etc? He's not even on prime Evra level. So he's not even our fastest left back.
When talking about our fastest players, it has since 2010 been Valencia, Rooney, James, Smalling, Rashford, Lukaku, Dalot who's been mentioned as the fastest players in the squad. I imagine Højlund being up there now. Shaw was mentioned as having one of the highest top speeds at one point, but he has never been that quick. It has been asked many times, but I've never heard Shaw mentioned much in these discussions. He probably does have the best first touch though - and that matters just as much. He's always struggled against very quick players.