Used car dealer CarMax is trading near its all-time high ahead of its quarterly earnings report, due out Friday morning.

BK Asset Management's Boris Schlossberg told CNBC's "Trading Nation" on Wednesday that Wall Street will be watching for the results with two overarching themes. Here's why:

• Principally, market watchers could gain insight into the state of the consumer, since used cars are a primary middle-class purchase and could serve as a reliable gauge. If the numbers disappoint, this could be a warning sign that the state of the U.S. consumer is not as robust as the market thinks.

• The second major theme is whether secular trends in the automobile market are beginning to affect the company. In other words, if Americans' demand for cars is waning broadly, the stock could be negatively impacted.

•The stock fell on its last earnings report in April; CarMax reported quarterly sales that missed expectations, and net income fell year over year, so the market will be looking for a strong rebound for this report.

• Since CarMax shares are trading just under all-time highs and have run up nearly 19 percent in the last two months alone, the stock could see a meaningful pullback if the report does not deliver.

Bottom line: When CarMax reports quarterly earnings on Friday, Wall Street will be watching for a window into the health of the U.S. consumer and whether trends in the broader used car industry are affecting its business.