FWIW - I don't really believe you - the average man jacked will not be muscular at 260 unless you are 7 foot tall. There has been a lot of work done on a person's muscular potential and there is basically no one who is not using hormones who is going to be jacked at 260.
Martin Berkhan of Leangains.com has a somewhat simpler model than Casey’s, also based on his observation of top level natural bodybuilding competitors who are contest lean (e.g. 4-5% body fat).
His equation is:
Height in centimeters – 100 = upper limit of weight in kilograms in contest shape.
So take your height in inches and multiply by 2.54, that’s your height in centimeters. Subtract 100 and that’s your predicted maximum weight in contest shape (which is 5% body fat or less for males) in kilograms. Multiply that value by 2.2 to get pounds. So let’s look at body weight at 10% body fat using the same heights I used for Casey’s calculator. I’ve also calculated out lean body mass at 10% body fat.
So for example I am 76 inches tall or 193 centimeters - 100 ..so that's 93 kilograms. That's 204 of lean mass plus another 20 pounds of fat (10 percent or so is reasonable for an athlete). So the most muscular and lean I could possibly be is 224 or so pounds.
So yeah lose some weight - and stop kidding yourself. Unless you are extremely tall and muscular and are a pro bodybuilder you aren't going to carry that kind of lean mass.
There was one D1 college linebacker who was a very good tennis player. He was pretty ripped at 240 or so (probably with some chemical help). But even he admitted he should lose some weight to play better tennis.
The big problem is that running around on concrete increases the shocks to your joints. Muscle on your legs does some to offer some cushioning - but the muscles in your upper body just seem to mostly add to the load.
If you look at the quickest all around athletes - most of them are only 200lbs or so - we are talking about pro level cornerbacks. Because the average man is only 5'10" this is right where you want to be - lean and at 200lbs or less.
Rule of thumb - can you see a six-pack. If you can't you are well above the 10% where you want to be. You don't need to get all fancy and get body fat testing and so on. I'd add that unlike NFL cornerbacks we play on a hard surface so its probably even more important that tennis players be thin.. I'd absolutely give up some muscle to stay lean for tennis.. Federer is a skinny dude - IRL. Lets be clear about this. If you get a chance to see him up close and personal - skinny.
They had this guy going around measuring biceps of players. One pro player had a bicep of 12.5 inches - a lean guy no doubt but that is seriously skinny.