Or just train more efficiently. It has already been said that multi-skilled players will have lower salaries.
The only reason that 'multiskilled' players are having lower salaries is because their skills are lower. Since centers are mostly trained in 3 or 4 skills, those skills will be higher because you will train less skills.
Salary increases way more at higher skills than at lower skills.
Guards are trained in more skills, which makes their skill level lower, that's why the salary is lower atm.