Is your hamstring used while playing football?

Answer 1

Yes. The hamstring is a tendon that connects the knee to the muscles of the thigh and is used in running.

"In human anatomy, a hamstring refers to one of the three posterior thigh muscles, or to the tendons that make up the borders of the space behind the knee. In modern anatomical contexts, however, they usually refer to the posterior thigh muscles, or the tendons of the semitendinosus, the semimembranosus and the biceps femoris." - Wikipedia 15/10/09
The hamstrings, as a group, act over the backs of 2 joints - at the back of the thigh and behind the knee.

The hamstring is important during running and walking especially. The hamstrings also assist deceleration when the knee is ballistically (forcibly) extended - as in slowing the leg down after kicking the football and in returning it back to the ground.