Originally Posted by tyu1314
You can also string up the backup with gut, it would remain its playability until it break.
I wouldn't recommend that to anybody. Guts have a sling shot feel and behave different to poly. You have to get used to them. Not a good idea if you break one racket in the middle of the match and now you have to play with a complete stranger. If you only have two rackets, then I would recommend to string them with the same type of string and same tension. If one breaks, the other will feel just the same. You want consistency.