#3 Mata will provide a variety of options to Valverde
Valderde clearly doesn't categorize underperforming Andre Gomes as a long-term stalwart which will make easier for Mata to get minutes at Camp Nou. Mata still has a lot of football left in him. He's tireless ball-winner which is one of the reasons he has survived at Old Trafford which will help Valverde recreate his dynamic pressing system.
Mata boats enough quality to help Barcelona regain their European supremacy. He can play in both 4-4-2 and 4-3-3. He can form a midfield of Phillipe Coutinho, Sergio Busquets, Ivan Rakitic and him just behind Luis Suarez and Lionel Messi in a 4-4-2 taking the burden of creating from Messi's shoulders.
In a 4-3-3, He can sit right behind Suarez and interchange roles with Messi providing stability to the midfield. The Catalan club would've unreal and electrifying depth with Mata.
Valverde could help Mata unleash himself playing in a free-flowing side like Barca. With club legend, Andreas Iniesta leaving Camp Nou leaving a void which cannot be replaced, Mata can replace him with ease. He is quick, agile, forward thinking and has exceptional passing abilities.