Many people have better success when playing against "hard"
hitters than they do against "soft" hitters. The main reason
is that you are just returning power that a hard hitter is
giving you. When playing players that don't hit with power,
you probably try to generate too much power, and this changes
your swing and normal game.
You have to decide to play your game and your style without
over hitting or becoming too aggressive. However, you don't
want to try to "soften" up your strokes so much that you are
playing your opponent's game.
In my opinion, footwork is a major factor when playing a
softer hitter. When your opponent doesn't give you power,
the ball doesn't arrive to you as quickly. Many people
struggle because they don't move to the ball. They wait for
the ball to come to them which it does more slowly. When
this happens, players usually make a faster swing when good
footwork would help solve the problem.
Another major factor is the mental game. How many times
have you thought, "how can I lose to this guy? He doesn't
even really hit the ball!" You have to stay focused, play
your game, and remember that it's just a different style of
play that you must make strategical and mental plans against.
If you could hit "soft" shots and beat Sampras wouldn't you
I would encourage you to practice against as many "soft"
hitters as you can. Personally, as a collegiate player, I
went through the same pains. I played great against a highly
ranked serve and volley aggressive player and fell apart when
playing the consistent baseliner that no one had heard of.
You are not alone in your difficulties with this type of player,
but you've probably learned to adjust against opponents with
different types of spin, pace, and direction and you can
also learn to overcome the "soft" hitter.