Rafael has said that the signings of Robin van Persie and Shinji Kagawa helped Manchester United win back the Premier League title.
The Red Devils reclaimed the trophy from Manchester City, finishing 11 points ahead of their local rivals in the table.
The Brazilian told the club's official website: "I think we were extremely focused this season. I think we have had the mentality to get the trophy back. Everyone worked together.
"Robin coming in has helped a lot as well, Shinji Kagawa too because he is also such a good player. The players we brought in helped ensure the spirit of the team is very good.
"[Kagawa is] a clever player. Maybe it's always hard when you come over and it's been the first season for him. He is Japanese and played in Germany, where it's a completely different type of football. But he's a clever player and shows this in training."
Van Persie scored 30 goals in all competitions last season, while Kagawa netted six times.
