I haven't read any Tomiyasu rumours prior to today, but if tendonitis was supposed to be his original injury, then the fact he's still out means it's tendonosis.
Once tendon collagen degrades in chronic cases, the fibre separation is usually filled by junk ground substance and junk veins - which is ok for everyday folk but not so much for high level athletes. If he's lucky, he's responding well to physical therapy like eccentric strengthening, which may leave his collagen in a healthier state than the DMZ it resembles now.
Rosicky, IIRC, developed tendonosis in the 07/08 season and came back less than half the player. It's not the player's fault unfortunately. The human body has crude repair mechanisms and there is no guaranteed treatment to fully reverse damage caused by tendonosis.
