In the first quarter, Dirk Nowitzki took exception to Serge Ibaka gently touching his face while he attempted a jumper. Nowitzki spent some time jawing with Ibaka following the play, which Ibaka shrugged off because it was largely incidental contact and Nowitzki has a history of enjoying loudly complaining about things. On the ensuing Thunder possession, however, Nowitzki got into an unnecessary shoving match with Kendrick Perkins under the boards and tempers flared over, earning both men a technical foul for their troubles. See the whole sequence of events in the video below.
Tempers certainly won't be cooling off any time soon, as this series still has a long way to go.