Manchester United and Chelsea are rocking the English Premier League boat, as the two sides are close to completing a major transfer that would send 25-year-old attacker Juan Mata to Man U, a direct competitor.

Since Jose Mourinho took over at Chelsea, Mata has fallen out of favor. He's started in just half of Chelsea's Premier League fixtures, with other players such as Eden Hazard, Oscar, Andre Schuerrle and Willian eating up most of his minutes. Chelsea is also reportedly trying to sign Everton forward Ross Barkley, which would render Mata even more expendable.

In 13 Premier League matches this season, Mata has yet to find the back of the net. He's got 11 shots to his credit this season with no goals and just two assists.

Despite his dwindling contributions, shipping Mata to a fellow Premier League side surprised Arseanal boss Arsene Wenger. "I am surprised," Wenger said. "Juan Mata is a great player and they sell a great player to a direct opponent. It opens again a little bit the opportunity of this transfer market because Chelsea has already played twice against Man United. They don't play against them anymore. They could have sold him last week [before United's 3-1 defeat at Stamford Bridge].

"If you want to respect fairness, that should not happen. You would want that everyone is on the same level. Chelsea do not do the rules. Maybe the rules should be adapted to more fairness."

ESPN is reporting that Manchester United was not Chelsea's first choice to sell Mata too; their story mentions Paris Saint-Germain and Atletico Madrid as preferred destinations that didn't pan out. Also, ESPNFC.com's Gabriele Marcotti writes that as long as Mourinho was boss, his bid to be a part of Spain's World Cup team would be in jeopardy.

"This is a World Cup year and simple math comes into it: Spain are absolutely stacked with talent, he's on the fringes as it is and needs playing time to make his case -- or he won't be going."