it can take a while to get that tunnel vision in a match, sometimes it doesn't show at all
tonight i played someone who hit continental and lots of forehand slice, took me a while to find out how to play him and while I was up 2-1 early, quickly found myself down 5-7, 0-2 and 30-0
slowly I just worked my way back, focusing just on the ball from the time it left his hand and through my contact point and what needed to get it done.
finally after 21 + games, my serve showed up and I lost about 5 points on it the rest of the way, closing it out 5-7, 6-4, 6-3
find a spot for your thoughts, I was trying to get into it, talking to myself, moving, but in the end wasn't focusing until I just cleared my head and started focusing on hitting tight to his backhand