I think that cheats are possible, but I am persuaded that
this type of cheat is not possible beyond the limits mentioned by ManuTOO. After all, he programmed the game, and I doubt that he is wrong. Numerous times I have
observed changes in the game only to find out that these things had not been changed (maybe I was right 1 of out 10, as there was maybe once or so when ManuTOO posted a

or a

with a comment that he had verified an issue).
I've been reticent about the other types of cheats, although I've mentioned them some, out of concern that my mentioning them would increase their usage. However, I'm past that now, as they are already too common. Induced lag is plaguing matches, and this is difficult to combat as the games are hosted peer-to-peer. Anyone interested may read of these cheats affecting several other online tennis games (titles) (I won't mention them, but they are popular titles, and posts about these cheats appear in forums for these games). You can search YouTube for
standby cheat or
lag switch and you will see videos of matches with games such as
Halo and
Gears of War in which this cheat was used. There are also videos there of how to make a lag switch, although some modems have a standby button which may be used instead. This is nothing new. Actually, there is a market for this, and places are selling lag switches now. I've played many matches where
"... paused the game" will flash while the online game is being played (and action is continuing), and many other strange things have been observed. Sometimes, the ping will be great (100 ms - 160 ms), but my movement will be extremely slow and my opponent's movement will be normal; or the ball will come toward me at a normal speed, but my movement will be much slower than normal. Sometimes, I'm sure just a bad connection without induced lag is the cause, but many times, it is caused by my opponent's cheating.
It would be great if there were an option in TE2009 to end a match if the transmission from the opponent ceases to be received by the other player yet the transmission from the other player is able to be sent to the opponent (as with a lag switch, the wire that sends the data from the one using the lag switch is made open, while the wire that receives data from the other party remains intact). I don't know of a solution for this induced lag issue, but denying that it is a problem is not the solution.