Second: FORGET ABOUT BUILDING TOO MUCH MUSCLE. You arent going to build a ton of extra mass unless that is exactly what you are trying to do. Also you can afford to gain alot of mass without interfering with your performance. I don’t know why lots of people think muscle is going to slow you down.
If your seriously worried about added mass hindering your performance, test your verticle jump/broad jump/pullup reps. All these are effected by strength AND weight
Think about it this way: if you doubled the strength of all the muscles that contribute to your jumping ability, that would probably only add 20-25% to your total weight. That means you can jump at least 60% higher.
Megaditto all the above posts. You’re not going to get slow and inflexible unless you train slow and neglect your flexibility. Big Ron Coleman (yes, that Ronnie Coleman) can do the splits at age 40+. Ernie Taylor is another pro bodybuilder that is 36+ and still does martial arts and can get the splits.
Besides, the quickness you’re talking about as a goalie is largely “first step” quickness, or quickness over short distances. Way back in the day, the Russkies took elite olympic weightlifters and test them in the sprints and some other track tests. They found that the lifters were just as fast as elite sprinters out to about 15 meters. They just didn’t have the muscular endurance or technique to keep getting faster in the sprint. If you’re still worried about getting all slow, think of NFL wide receivers, and cornerbacks, and linebackers. All bigger and muslced up, all fast, all powerful.
Train equal parts muscle growth, strength, and speed, and do dynamic flexibility training after weights and at other times in the week. Problem solved.
You’d do well to add 25-35 lb of muscle. 6 foot 150lb pounds is a string bean.