Apple Inc. (NASDAQ:AAPL) will release its next earnings report on Wednesday, and Philip Elmer-DeWitt of Fortune has taken note of a particular segment of the company’s revenue which analysts believe will significantly slow down. He’s talking about revenue for the iTunes, Software and Services segment. If they’re wrong though, there could be room for upside to consensus estimates—as long as weakness in other areas isn’t worse than expected.

Apple iTunes Radio

Good news about Apple’s iTunes

The iTunes, Software and Services segment includes—according to Apple Inc. (NASDAQ:AAPL)’s previous earnings statements—revenue not just from iTunes itself, but also the entire App Store, the iBookstore, licensing, AppleCare and “other services.” Elmer-DeWitt calls the segment Apple’s answer to Facebook Inc (NASDAQ:FB), Amazon.com, Inc. (NASDAQ:AMZN), Google Inc (NASDAQ:GOOG) and others in those spaces because it covers a wide array of areas.

He notes that iTunes itself is actually a growing business, generating over $16 billion in revenue during the 2013 fiscal year, which makes that segment’s revenue alone fall between that of General Mills, Inc. (NYSE:GIS) and The Gap Inc. (NYSE:GPS) within the Fortune 500. That alone is quite a feat.

And the bad news

Unfortunately though, this segment of Apple Inc. (NASDAQ:AAPL) hasn’t seen the same level of growth competing Internet companies have experienced. The author notes that of the 29 analysts who submitted estimates for the iTunes division, the growth rate of the segment is expected to be less than half of 2013’s growth rates.

In this week’s earnings report, the average estimate for growth in Apple Inc. (NASDAQ:AAPL)’s iTunes segment is a 10.6% year over year increase to $4.55 billion. In the same quarter a year ago, the growth rate of the segment was 26%. Even the analyst who had the highest estimate for growth in the segment is projecting $4.94 billion, while the analyst who is expecting the least projects just $4 billion—a decline of almost 3%.