The last few years have been challenging for Richfield-based Best Buy, amid management shakeups and a tough climate for retailers everywhere. CEO Hubert Joly gets most of the attention but McCollam, who joined in 2012, is another central player in the effort to overhaul the company. She doesn’t talk much to the press, but McCollam was already respected and admired on Wall Street as a sharp retail executive. She served as executive vice president, CFO and COO for Williams-Sonoma from 2006 to 2012, and also served on the board of OfficeMax. McCollam has been instrumental in paring expenses from Best Buy’s ledger to improve the company’s cash flow. Best Buy remains a work in progress, but retail watchers have strong faith in McCollam’s acumen.