First, I refer you to Dan John, Jim Wendler and John Welbourne. They all have a lot of experience in the weight room and training athletes.
Second, how you build your program is based on your goals. If tennis is your priority, then doing weights afterwards is fine. If weights is your priority, than depending on how intense your tennis is, you might need to spread them out.
General rule of thumb for most in the weight room is 3-5 exercises for 3-5 sets for 5-12 reps 3-5 times a week. How often and how much depends on your training experience, how well you recover and your goals.
Ideally wanting sets to be fatiguing, not necessarily to failure but close to it (maybe 1-2 reps in the tank).
Just training full body two times a week can be adequate for those just wanting injury prevention and muscle retention. Someone wanting to take things to another level will need 3-5 times.
As one advances you can experiment with various splits like upper/lower or push/pull/legs.
When doing full body I think about hitting a pressing movement, hitting a pulling movement, hitting a squat movement and hitting a hinge movement (deadllift for example). And possibly an accessory exercise for each.
If doing upper/lower split I think about pulling vs. pushing for the upper body day and then anterior chain vs. posterior chain for the lower body day.
In terms of exercise selection I focus on compound movements--which can be done with barbells, dumbells, kettlebells or machines. Compound movements hit a group of muscles instead of isolating single muscles. But focus on compound exercises and if having time and energy you can add on some isolation stuff--usually for fun. k
When I train 4-5 times a week I typically build in some prehab exercises into the plan--external rotations, neck work, calf and ant tibials work, core work.
When I train 2-3 times a week, on the off days I'll do the prehab exercises since they aren't draining or demanding.
Plyometrics are overrated and really have value once you have built up a good stength base. Strength is the foundation for almost all power movements. If you are weak doing box jumps is just going to stress your body out. IF you are strong, box jumps will train your body how to use all the muscle you built. If you spend a lot of time on court and work hard, you are getting in a lot of plyo work--running and jumping, short turns and hops is what plyo is. So adding additional plyo workout might lead to injury if your on court time is pretty high. If you do add plyo work, go very slow and use a very low volume approach that grows slowly. Muscles can heal pretty fast, tendons are much slower.
Now to layer this into your tennis schedule again depends on your goals and priorities.
As bad as I am at tennis, in the summer I'm fortunate to play 3-6 times a week. So it would be hard to flip flop weigths with tennis. But I also realize this effects my total ability to recover.
I'm currently weight training 3 times a week. I never do a hard workout right after tennis. I usually have at least 4 hours between tennis and strength training. Ideally one in the morning and the other in the evening (allowing time to fuel and rest). If I have to do weights and tennis back to back, I find I can play tennis decently after an upper body workout. A leg workout can be a different story, maybe some light hitting, but if it is hot out and demanding, going on the court after hard lower body work is tough.
If you play tennis a lot think of an AM/PM set up. If you only play a few times a week, then it would probably be better to alternate them. Either way if you are either playing tennis or hitting the gym on most days, think about having a day off of both to help with recover.
Recovery is also key. Tennis takes its toll on recovery. There is a reason pros don't look like the Rock, hours on the court is draining especially at the level of intensity they play. So make sure you are getting at least 8 hours of sleep nightly, limit alcohol which kills recovery (as well as other drugs including goofy energy drinks or heavy caffeine use), make sure you are eating and getting protein and hydration. In addition psychological stress can slow down gains--so don't overwork or burn the candle at both ends. Some light aerobic work can be helpful to build the recovery system. Cycling for 10-20 minutes after tennis can be helpful. Walking on the days you don't play tennis outdoors can be good for recovery too. I think of the aerobic system as the repair/recovery system that lets us do aneaerobic demands more often. The better your aerobic system the quicker you can hit heavy weights, the shorter time you'll need between hard points in tennis. Again, keep in mind if you are hitting the courts 4-6 times a week for 2 hours drilling intensely or playing singles intensely, you probably don't need a lot of long aerobic work, just some supplemental stuff to help with recovery.
