The Spaniard moved to the Allianz Arena for a Bundesliga-record €40 million fee in August, and subsequently made his debut in his side's 6-1 win over Stuttgart as a late substitution.
And the former Real Madrid trainer is delighted with his new acquisition, but was quick to urge the 24-year-old to work hard to secure more playing time.
“He’ll be a huge bonus for us in football terms," he told the club's official website. "He gives us even more quality in midfield, which is a motivating factor for everyone.
“But even Javi will have to play and fight his way into the team based on his performance. Obviously he has my full support, just like all the other players.”Bayern's next match is against Mainz on Saturday, with kick-off scheduled at 15:30CET.