The solution is, fill your squad with 22 players, 11 main players, just 5 good subs, the rest shall be 3 *, 4 * (up to you), after main matches you gotta play in a day, arrange sơm friendly matches to earn money from tickets, merchants etc (you can get extra packs as well) without worries that your main player will be injured.
Well, to be honest, there is a better solution as you can use token to sign free agent players (or player with high value but with low purchase cost and sell back).
good luck