Costa In Bust-Up With Oscar  (Sky Sports)

Chelsea duo Diego Costa and Oscar had to be restrained during training on Wednesday after Costa floored the Brazilian with "a particularly strong tackle", Sky sources have confirmed.

The pair clashed angrily after Costa's challenge on Oscar, who was understood to be unhappy with the strength of the tackle.

The incident happened in what has been described as a "highly competitive" training session at the club's Cobham base.

Team-mates and coaching staff stepped in to calm the situation down, although later on in the session Oscar responded with a hefty challenge on Costa in retaliation, temporarily igniting the situation again. Once more, the pair were separated.

No punches were thrown and the pair are understood to have settled their differences on the pitch, with witnesses telling us they walked off the pitch together, laughing as they went.

Guus Hiddink, the club's interim manager, is understood to be relaxed about the situation, content that both players left the pitch with no lasting animosity.

Oscar has since played down the incident, stating via his official Twitter account: "He's one of my best friends and never fight."

Costa has endured a difficult second season in the Premier League, having scored only six Premier League goals to date.

He threw his bib in the direction of Jose Mourinho during the draw against Tottenham, and was booed by Chelsea fans in the first game after Mourinho's sacking.

However, Mourinho's departure has coincided with a return to form, with Costa having scored three goals in Chelsea's last two matches.