With U.S. equities faltering and September and showing few signs of breaking out of that slump through the first few days of October, this should be the time that investors warm to consumer staples stocks and exchange traded funds.

However, investors may find that faith is unwarranted with the defensive sector currently looking somewhat extended on valuation.

To be fair, the Consumer Staples Select Sector SPDR (NYSEArca: XLP) was not a dreadful performer as U.S. stocks dithered last month. However, XLP did finish September with a modest loss of 0.1%. That in a month in which XLP is historically one of the two best of the nine sector SPDR ETFs. [September’s Best Sector ETFs]

Still, XLP, the largest staples ETF by assets, is down nearly 1% over the past 90 days. Although that is better than the S&P 500 over the same period, the performance is not doing much to stoke confidence in the expected durability of the staples sector.

In a recent research note, AltaVista Research tagged XLP with an underweight rating, making the ETF the only one of the nine sector SPDRs the research firm labeled with that ominous rating. The Energy Select Sector SPDR (NYSEArca: XLE) was the only one of the nine SPDRs to earn an overweight rating from AltaVista while the remaining seven are rated neutral. [Value With Energy ETFs]