How can I clean stains from sisal flooring

Flooring still looks good after 7 years apart from staining where hubbie sits - his dirty shoes and slitterins have marked an area about a foot square. Any suggestions re cleaning this small patch?

Here's a web page. Make sure to read the warnings. Some cleaning products that work on synthetics will damage natural fibers.

http://www.sisalrugs.com/how-to-clean-sisal-wool-rugs