Leak in center drain

[ddt3]

I have just cleaned my pool completely out. There was no leak before I started. I filled it up and noticed that the yard is soaking wet. I think it is leaking some where at the main center drain. I can see where the dirt has dropped from the center drain to the outside of the pool where the drain line runs.
I guess my question is, can you repace a center drain without replacing the liner? I do think the drain is cracked somewhere under the cover. I plan to plug the drain first and see if it stops, this will tell me if it is the line or not. Any helpful suggestions will be fine. I have a 27 foot round 48 in. tall pool it holds aprox 17,000 gals. water. My e-mail address is dennytesst@nctv.com If anyone has a simple suggestion or something please help. Thank you.