Was Michael Crabtree's left foot injury a new injury or a preexisting condition?

Michael Crabtree left Sunday's game against the Eagles with a foot injury, but returned after missing one drive. Crabtree was spotted on the sideline working with trainers and rolling a ball beneath his foot, suggesting that he may be dealing with a plantar fascia issue.

Fox Sports' Mike Garafolo tweeted:

Appears to be a plantar fascia issue for Michael Crabtree, what with him rolling his foot on the ball and pointing to the arch.

— Mike Garafolo (@MikeGarafolo) September 28, 2014

Rolling a ball beneath your foot is indeed treatment for plantar fasciitis. However, considering Crabtree's surgically repaired Achilles tendon, it is most likely ongoing treatment related to the Achilles injury.

If you point your toes or flex your foot, it is the calf muscles that allow the movement. The calf muscle also allow a person to push off while walking, running or jumping. The Achilles tendon is actually an extension of the calf muscles, which extend down and under the heel.

Extending from the heel to just behind your toes, plantar fascia is the sheath of connective tissue that covers the muscles on the bottom of your foot. The same tissue extends over the heel and becomes the Achilles tendon. The entire tissue allows you to flex your foot and curl your toes.

Pain on the bottom of your feet is often due to tightness in your plantar fascia and Achilles tendon. Considering Crabtree's medical history with his left foot, a tight Achilles tendon is very likely the cause of pain on the bottom of the foot. To relieve the pain, a foot brace holding the foot in flexion (usually overnight) elongates and loosens the tendon.

If he was experiencing tightness in the Achilles tendon, a preventative measure to avoid further injury is proper stretching. When you massage the sole of your foot with a ball, you loosen the starting point of a network of connective tissue that runs all the way up your back of your body. In fact, many athletes with chronic hamstring issues get relief from pain and loosen tightness in the hamstrings by rolling their feet on balls.

Regular ball rolling releases tension in the muscles and fascia. Since the fascial body is a web of connective tissue, a release in one part can trigger release in the entire web.

Therefore, it appears Crabtree did not suffer a new injury to his foot. Rather, there was some tightening, and he engaged in typical ongoing physical therapy exercises which keep his Achilles healthy and loose. Considering he returned to the game after one drive, it appears this is indeed the case.