Matias may not yet be a household name in England, but he has the potential to be, already a well established player in Portugal.
The attacker joins new Portuguese coach Carlos Carvalhal at the club, with his addition a demonstration new owner Dejphon Chansiri is prepared to invest to help the club challenge for promotion.
Matias scored 20 goals in 36 games for Nacional, and Wednesday have beaten off competition from the likes of Malaga and Besiktas to land his signature.
17 of those strikes came in Portugal's Primeira Liga, and he was the highest scoring Portuguese player in Europe last season apart from Ballon d'Or winner Cristiano Ronaldo.
His goals were just four fewer than Porto's Jackson Martinez, who has just completed a £25 million move to Atletico Madrid. Matias' fee is around £2 million.
Able to play as an attacking midfielder, winger or up front, Matias is likely to rejuvenate Wednesday's forward line, which was one of the most uninspiring in the Championship last season.
His addition is a real coup for the Owls, and the signs are that their spending spree is only just getting started.