Estimates for fourth-quarter earnings per share have been dropping like a stone for Advance Auto Parts (AAP 0.58%). Meanwhile, estimates for competitors AutoZone (AZO 0.03%) and O'Reilly Automotive (ORLY -0.97%) have held steady. With Advance Auto Parts trading near all-time highs, and trouble brewing with the companies' earnings estimates, perhaps it's time to consider taking some profits based on what may be brewing beyond the results. 

Results
Advance Auto Parts reported its third-quarter results on Oct. 31. Total sales inched up 4.3%. Same-store sales slipped 2%. Earnings per share popped 17.4% to $1.42. Overall, the results were not too bad at first look.

Darren R. Jackson warned, "We are pleased with our profit improvement in consecutive quarters and remain cautious on the underlying sales environment." He stated that they'll be "making the necessary adjustments" to improve profitability. On the one hand, improved profitability is always great. On the other hand, the word "adjustments" sounds like there may be challenging times ahead that warrant layoffs or some other cost reduction moves.

Advance Auto Parts is acquiring General Parts International. There certainly could be some consolidation of staff related to that deal. CFO Mike Norona characterized the current state of the market as a "softer sales environment." He said the increase in EPS was due to "disciplined focus on expense management." He expects the softer sales environment to persist into the fourth quarter.

Conference call
In the conference call, Jackson stated, "The overall market continues to face headwinds from a backdrop of limited consumer spending as the consumer appraisal of the economic conditions continues to affect consumer confidence." He blamed uncertainty regarding the government, Obamacare, and the economy all contributing to weakness going forward which is causing consumers to perform "repairs that are absolutely necessary to keep their vehicles on the road."

Advance Auto Parts is experiencing competitive pressure as well. Jackson pointed out that 80% of new store growth from competitors in the last 12 months has been within the footprint of Advance Auto Parts. This implies competitors are challenging Advance Auto Parts head on and making some degree of progress at successfully stealing customers away.

Stacking up against AutoZone and O'Reilly Automotive
AutoZone's next quarterly earnings report is scheduled to be released Dec. 10. In its prior release, adjusted sales were up 5.6% overall and up 1% on a same-store sales basis. AutoZone opened 69 new stores during the quarter. CEO William Rhodes stated, "We continue to see significant opportunities for new store growth." In the US alone, AutoZone opened 153 new locations this year. The "significant opportunities" in terms of store growth could involve more chipping away at Advance Auto Parts' market share.

O'Reilly Automotive last reported its results on Oct. 23. Sales jumped 8% to $1.73 billion. Same-store sales shot up by 4.6% in stark contrast to Advance Auto Parts' 2% decline. CEO Greg Henslee said the 4.6% gain was "industry leading." He also said O'Reilly Automotive is on pace to open 190 net new stores for 2013. They are "very pleased with the strong results we continue to see from our new stores" and are targeting 200 new stores for 2014.

Foolish final thoughts
It appears that Advance Auto Parts' loss may be due to AutoZone and O'Reilly Automotive's gains. Pay close attention to the earnings report and conference call from AutoZone for more clues. Advance Auto Parts may be in the early innings of significant sales losses to its larger rivals.  Foolish investors may want to consider stay on the sidelines until the picture is more clear with Advance Auto Parts.