Get a substring from a specific pattern in an XML string

I have a string in XML that will look like below:

NNNANNNNN.NNNNNN

Where N is a numeric value (can be as long as 10 digits) and A is a single Alphabet.

What I need is to get the string after the Alphabet and before the decimal value and return the value with leading zeroes (10 characters max with the extracted value)

For Example I have

123A123456.789 

then the result will be

0000123456

Can anyone point me in the right direction using XSLT 1.0.