The England Under-21 midfielder had an extended summer break following his involvement in the European Under-21 Championship in Denmark, and then missed last Tuesday's trip to Werder Bremen with a chest infection.
He told the club website: "I have not had a lot of pre-season because I had those few extra games with the Under-21s and then I also had a bit of an illness last week so it was good to get out there and play the full 90.
"Generally I feel really good though. I trained hard last week and did lots of running so I feel as if my fitness is really getting there now.
"It was a hard game for us as Villarreal are a really good side who regularly finish high up in La Liga. But we are still warming up for the new season, we will take the positives."