The 23-year-old defender wasn't overly expensive (roughly £3.9 million), and Sir Alex Ferguson has brought him in to back up Patrice Evra. Evra recently turned 31, and with Fabio da Silva on loan with the Queens Park Rangers, United needed another quality contributor off the bench.
Assuming he passes the medical, Manchester United got exactly that in Buttner. He is an aggressive and speedy left-back who has the talent to develop into a full-time starter when Evra departs.
Buttner was a fixture with Vitesse, making at least 23 appearances in each of the last four seasons. Last year, he played in 32 matches, anchoring a strong Vitesse defense that allowed the fourth-fewest goals in the Eredivisie.
Since he is a bit raw, Buttner must improve some of the more technical aspects of his game. He is susceptible to getting caught out of position, and he will need to adjust to the higher level of play in the Premier League.
Although it may take a little while for him to get comfortable, Buttner eventually should fit in nicely with United. He has good instincts, he can bail himself out of tough situations with his speed and, as you can see below, he occasionally will get involved in the attack as well.
As of now, you shouldn't expect too much from Buttner. I highly doubt he will take Evra's starting spot this year, but he should provide some insurance off the bench should the Frenchman struggle or suffer through injuries.
This is a good long-term pickup for United, and if Buttner is able to provide some quality minutes this season as well, his transfer will be viewed as a success.