Chris Graja joins Diane King Hall to preview Walmart (WMT) earnings. He says the outlook and guidance is the most important aspect for the big box retailer. He highlights the company's AA credit rating and strong financial position as a baseline for future growth drivers. Chris says the focus is now growing sales at each store rather than expansion of store presence. Compared to Amazon (AMZN), he weighs the e-commerce battle and says WMT "credibility could grow."