http://espn.go.com/espnradio/play?id=16769911

windhorst and amin do a good job of explaining it in this podcast (skip to about 17 minutes in; although the whole thing's worth a listen) but in short, what the thunder can essentially do, since they now have cap space, is renegotiate this last year on westbrook's contract to bump him up to a true max in 16-17, which takes him from 17m up to ~26m, and then extend up to 3 additional years, with an opt out after 17-18, when russ would have 10 yrs of service and thus be eligible to cash in on the super-max.

it would benefit both parties, okc gets an assurance of at least 2 more seasons of westbrook and can plan accordingly, and russ essentially gets a free extra 8m next season and still hits fagency after his 10.