After watching Seider's hit on Hagel it did appear that it was a clean. Hagel found himself focused on the puck and Seider took advantage his opportunity. Tampa Bay did well to stand up for Hagel and was probably ready to engage in some physical play after two not so great performances in consecutive nights.
These are the kind of hits teams can expect from Mortiz Seider nowadays. One of the reasons Detroit loves this German defender. Teams had better be aware of his presence and make sure you keep your head up. In addition to his playmaking skills, Seider brings a physical element to his game that Detroit surely needs. Wait until Seider becomes bigger and strong as he ages. He will be an even stronger force.