You need to have this fixed on your Tiagra.

I caught a black the other day that broke this reel and the small section of bronze COULD get caught in the main gear drive and cause your reel to lock up and you loose your fish.

Shimano has re-engineered the part from bronze to stainless and as you can see in the picture, the new part should be stronger.

Scott at Haddrell's has a few of these in stock, but I would imagine you need to drop them off to have this fixed. It is not a cheap fix but knowing it needs to be fixed and then loosing a big fish...