Manchester United started their season with a 1-0 win over Spurs on Saturday. Red Devils did not have the best game with the new look team still gelling in.
Spurs lost thanks to the own goal from their right back Kyle Walker.
The Spain international, a £37.1m acquisition from Chelsea 18 months ago, played the full 90 minutes at Old Trafford.
But Mata concedes the team have work to do ahead of Premier League clashes with Aston Villa and Newcastle plus a Champions League qualifying double header against Club Brugge.
“As you could see, it was not a brilliant game but you can understand that, it being the first one, there’s still a lack of rhythm,” Mata wrote on his blog.
“It wasn’t easy for any of the teams, and the pressure from our opponent made it hard to play a fluid game, but we managed to score in the first half and that goal was enough to get the three points.”
“There were a few positive things apart from the score.”
“Old Trafford saw the debut of many new players, and personally I think all of them had a good performance.”
“It’s exciting to see how quickly they get settled and the warm welcome they got from our supporters!”