Reports this week indicate that Amazon.com (AMZN 3.56%) is getting ready to expand its AmazonFresh grocery delivery service. The leading online retailer has been testing it in select Seattle neighborhoods for years, and now sources are saying that Amazon will expand into California later this year and 20 major metropolitan markets next year.

If so, Wal-Mart (WMT 0.12%) doesn't have any time to lose. It has an advantage right now that Amazon does not. Wal-Mart has thousands of local Supercenters, grocery stores, and warehouse clubs that are already stocking supermarket items. It just needs to beat Amazon to launch.

In this video, longtime Fool contributor Rick Munarriz explains why a seeming threat to Wal-Mart is actually an opportunity in disguise.