He has pace, but pace enables him to run onto the ball that's been played over the top of a defence, this is what Trips does too, not just about raw pace but the pass too.
I am referring directly the the ability to take on a player, dribble past him, the better footballers can do this. Trippier is incapable of doing this, he has NEVER taken on a player and beaten his man!! He can't because he isn't as good a footballer as Walker. Walker has far more strings to his bow, pace, ability to take on a player, lay the ball off to (play short) to another player, carry the ball into the box, turn the defence. Tripps whips in an early ball.