The duo are widely considered as the top two forwards in England, and while Mata stopped short of saying that Soldado had reached their level, he has insisted that his former Valencia teammate has started impressively since his arrival earlier this summer.
The 25-year-old told Sky Sports News: "Let's see, but I really enjoyed it when I played with him for Valencia and with the national team.
"I think that he is doing really well. Last season, he scored a lot of goals, and this season, he has started very well. He's very good."
Soldado has scored twice in his opening three Premier League appearances, both from the penalty spot.