According to Yahoo! Sports, Derek Fisher has officially cleared waivers and will suit up tonight in the Thunder's home game against the Clippers. The report also says that Derek Fisher will be the backup PG for Russell Westbrook, indicating he'll get playing time right away.
Given how lethargically the Thunder have played lately, I wouldn't be surprised if Fisher was set to play Day 1 in order to give the team a boost. I would also point to the immediate subbing in of Mohammed (and Perkins) as soon as they became available following the trade with Boston. Fisher is a veteran and has studied OKC's offense thoroughly (as the Thunder played with the Lakers in a playoff series 2 years ago), so, mentally at least, it shouldn't be too big of an adjustment.
How well Fisher will adjust to Oklahoma City's system is anyone's guess. They've struggled from three lately, but the struggle has been a case of poor timing rather than actual percentages, so it remains to be seen how Fisher can help. However, he has the entire NBA bag of tricks acquired through years of knowledge, so perhaps teaching the Thunder "the little things" will be his purpose. Regardless, we will find out some of the answers in a matter of minutes.