Parejo has arrived from Getafe.
He said: "He (Mata) has left like many other very important players have down the years and the team has continued forward with good results.
"As well as that, Valencia have strengthened well this summer and the team is there to continue fighting for the top places."
Regarding his own start to life at Valencia following his switch from Getafe, former Real Madrid youngster Parejo said: "I've adapted very quickly, much quicker than I thought, and this has been possible thanks to the rest of the team.
"I don't know where I will play. I've played some matches in one position and others in another, but I've felt comfortable in both."