If he weren't injured I would say Semi and a future pick
You could have two uninjured Semis and two future picks and they still probably say no.
Yeah it's lowball offer but I think people here are overvaluing Jeff Green. He is not a starting PF or SF in this league. If they are looking for a C in exchange they can't expect a starting caliber one.
He is the starting F on a team that is 33-18, leading their division.
As a starting F, he is averaging 15 points a game.
And that is while starting out of position. The only reason he is a PF is because they have Durrant. On most any other team, he is a starting SF.
He scores about as well as BBD but doesn't rebound as well.
Put him as a SF on a team that does not have two of the biggest volume scorers in the league, and I think he would be a much bigger scorer. He also is a very good defender, particularly against SFs.
Green is a heck of a player who has been underutilized in OKC because they have been playing him out of position. If he is allowed to play his position, I think he is probably a second tier starter in the league. Not quite an All-star, but a very good all around player.