A defender is usually tall and has a pretty bulky body. If you have good strength and can rule out the opposition with tackling skills, then the best place for you is center back or a defensive midfielder. A defensive midfielder must also be a decent passer of the ball in order to start an attack by passing to an attacking midfielder. An additional attribute for a defender is to be aggressive. Speed is not necessary but it will help to catch up with those frisky opposing attackers.
The wing of the pitch is an easy way through the opponent's defense if you have the speed. So if you're fast and can dispossess the man with the ball, try being a left back or right back. If you're fast and have good ball control/dribbling and are good at crossing the ball into the box, then left or right wing in a forward position is suitable. But if you're a forward winger, short passing is also important if you want to give the ball possessively to a teammate instead of just dropping a 50/50 ball into the keeper's box. Wingers will sometimes need to be a good finisher too since he is an attacker, so he'll most likely get a shooting chance.
The attacking midfield position is the hub of the team because they're supposed to play-make and create chances for their strikers to finish. Speed is not really a crucial aspect but you will need to be an accurate passer in order to run the play of your team. Ball control/dribbling is needed to cushion the ball every time you receive it. Stamina will help because as a midfielder, you'll be running back to your defense in support and take it forward often. Midfielders who can find the back of the net and are able to work with both feet will be very useful at times.
In order to be a deadly striker, you'll HAVE to have a powerful, accurate shot because those midfielders will be expecting you to be clinical after they work their asses off. Keep in mind that finishing and ball control/dribbling are the most important attributes a striker should have. Then comes sprint speed and stamina since you will keep moving and finding space for your men to pass to you. Most strikers are not too tall and bulky so they can stay flexible and fast, but it can be an advantage if you're a striker with the body of a defender. The opposing backs will show aggression so being a big striker enables you to fight fire with fire. It helps you have more power in your shots and more threat with your headers. But unfortunately, you won't have the speed the average striker needs. Although you are the main finisher as a striker, it's good to have some passing mentality in situations where the opposing defense closes down on you.
These are just the base attributes that players should have in different positions. Hope this helped.