Originally Posted by
cny-bikeman
You are correct that the spring end has broken, pretty clear that it can provide no tension if not anchored and the fact the derailleur freely moves back and forth confirms the problem. You will indeed need to replace the derailleur. A triple 9 speed should not be a problem, and even a 10 will not offer a lot of problems.
I tried that once and decided it was not good enough to foist on a paying customer. The narrower cage rubs the chain at the slightest hint of cross chaining. Shimano 2303 derailleurs are still available. Ask your local shop if they can order one from J&B Importers, part number 26308.
That spring anchoring nubbin breaking off is my number one cause of Shimano road front derailleur failure. It's more robust on the 10-speed units.