Arsenal manager Arsene Wenger is questioning the tactics around Chelsea's sale of Juan Mata to Manchester United.
The Spanish midfielder is expected to be unveiled at United in the coming days, after the defending Premier League champions reportedly paid a club record transfer fee for his services.
Wenger says it's unfair on the teams who play Man United before the end of the season.
"It opens the game a little bit, the opportunity of this transfer market, because Chelsea has already played twice against Man United, so they don't play again anymore.''
Wenger says the rules around player transfers could be hardened to make an even playing field for everyone.
