It seems to me that ESPN has a script. Talk about stats A after the 3rd game, Talk about Serena Williams during the 6th game. Talk about the childhood of player A during the 9th game. Talk about stats B in the 10th game. Talk about an unknown celebrity during the tiebreaker, etc.
Fine if the match is a 6-1 6-1 blowout, but not if a decent match is going on.
If you get ESPN 360 you can often get the matches without a commentary, depending on what court they are on.