Oscar and Diego Costa had to be separated by stunned Chelsea team-mates during a furious training-ground bust-up that threatened to descend into a brawl.
There were claims that the pair even exchanged blows at Chelsea's Cobham training ground yesterday (Thursday), but an eyewitness insisted Oscar and Costa were dragged apart -before the incident went that far.
The clash took place after Oscar made what was described as an "outrageous" challenge into the knee of Costa after the striker had initially gone in hard on him.
It was after Oscar's knee-high lunge that the pair squared up and had to be pulled apart by their shocked team-mates before angry words could turn into a physical scrap. While Costa has a reputation for losing his temper with his opponents, the training-ground incident was largely being blamed on Oscar - even though the pair swiftly struck a truce. A source told The Daily Telegraph: -"Oscar's challenge was outrageous, straight into the knee of Costa, and could have done him some real damage. That sparked a brawl -between them and the other players had to stop it."
Guus Hiddink, the Chelsea -interim manager, is said to be -relaxed about the incident that came in a highly-charged training session in preparation for Sunday's FA Cup third-round clash against League One Scunthorpe United.
Hiddink is also satisfied there will be no lasting resentment, as the brawl was already the subject of dressing-room jokes immediately after the session.
Oscar attempted to further -defuse the situation by later -tweeting a message that read: "He is one of my best friends and we would never fight."
Hiddink was already planning to rest some players this weekend and it remains to be seen whether both Oscar and Costa remain in his -starting team.
Costa had been booed by some Chelsea fans, who partly held him responsible for the sacking of former manager Jose Mourinho, while Oscar had struggled to make an impact this season under the Portuguese.
But Costa and Oscar have both shown improved form since the -arrival of Hiddink and were on the scoresheet in the 3-0 victory over Crystal Palace last weekend.
This is not the first training-ground bust-up during Chelsea's troubled season, as youngster -Charly Musonda was involved in a similar incident shortly before Mourinho's departure.
Despite the fact he and Oscar have settled their differences, the latest clash adds to the controversial incidents involving Costa, who came back for pre-season overweight, received a retrospective Football Association ban for lashing out at Laurent Koscielny and tossed a training bib in the direction of Mourinho after being dropped.
Oscar is regarded as one of the quieter members of Chelsea's squad, but he became deeply -frustrated under Mourinho and his challenge on Costa was said to be rash and dangerous.
Radamel Falcao was back at -Chelsea's training ground -yesterday, having travelled back to Monaco this week as the London club look to cut short his ill-fated loan deal and create space for a new striker. Colombian striker Falcao is -understood to have spent Tuesday and part of Wednesday at Monaco's training centre to have checks on his injured thigh.
Chelsea want to end Falcao's -season-long loan early, but Monaco need to be sure of the 29-year-old's fitness before taking him back after Hiddink last week revealed he had suffered another setback.
Falcao has been out with a thigh injury since Oct 31 and broke down again in a training game.
Major League Soccer club -Columbus Crew are interested in signing Falcao, but their season does not start until March.
Monaco, however, were keen to check on the condition of Falcao before possibly taking him back -until March or until the end of the season, when they will look to sell him.
Falcao wants to play more -regularly over the second half of the season. Despite Chelsea -convincing him to take a 50 per cent wage cut to move to Stamford Bridge, his season-long loan has -already been an expensive failure as he has started only one Premier League game and scored one goal in all competitions.
Chelsea hope to free space in their squad and the club's wage bill by ending Falcao's loan so they can push ahead with plans to sign a new striker this month.
Leicester City striker Jamie Vardy is among their January, while Jackson Martinez, who is out of favour at Atletico Madrid, is an attractive loan option.
Chelsea would rather keep Loic Remy, who is a target for a number of clubs, until the end of the season.