Turn cards Pro by transforming common cards into better versions of themselves. To do this you will need three extra copies of that same player at the same tier along with a contract card. The main player will also need to be at max level, which may vary as it will depend on its rarity. Remember when you do this that the contract and the duplicate player cards are consumed in the process. Once cards are fully leveled Pro versions they tend to be competitive with or even better than the next tier of cards.