The incident at Cobham, which saw Spain international striker Costa take exception to a challenge from Oscar, was laughed off by the two players and the rest of their team-mates
And Hiddink joined in the fun on Friday, comparing the two players to bulls and suggesting Oscar should receive more physical treatment as he believes the Brazil playmaker benefits from becoming angry
Hiddink said: "We try to punch him every now and then to get him on this level
"When this guy puts the emotion in, then automatically his level of play rises.
"It was a pity that our photographer had a day off because he could've shot beautiful pictures of two bulls who were chesting a bit after a charge from behind from the smallest bull of the two, which was Oscar
"He got Diego
Then they stumbled over the ground, stood up as a normal reaction and then chested a bit without any further threat of punching or whatever.
"We came in between, but there was no need to say we had to grab them to avoid them hitting.
"Oscar apologised in front of the group
They looked at each other and then they started laughing
Jokes were made afterwards."
The Dutchman declined to take sides when asked who would win a hypothetical fight between the pair.
He said: "Diego looks the bigger bull, but Oscar might be a very fast, sneaky bull to make punches."
Hiddink's previous spell as interim boss, when he replaced Luiz Felipe Scolari in 2009, ended with him lifting that season's FA Cup at Wembley
A second win in the competition is an aim for Hiddink.
He added: "Fourth place in the Premier League is difficult
Then there are two targets left and one is the FA Cup.
"It's a big target for this group of players to get it."
Scunthorpe captain Stephen Dawson wishes it was former Chelsea boss Jose Mourinho in the home dugout on Saturday as he thinks successor Hiddink has got the Blues focused again
Asked whether the tie is more difficult than when the draw was made in December, Dawson said: "Yeah, I think so, if you look at the sort of run now and the way they are playing.
"I think their manager stressed about doing the ugly side as well and I think they did it well last Sunday (against Crystal Palace).
"I suppose the only plus side is I don't think (Eden) Hazard is playing, so it might give us a bit of a chance, you know?"
Source : PA