If Apple misses this key number, it means Tim Cook is misjudging his business

Apple reports June quarter earnings on Tuesday, and they're expected to be muted - one Wall Street analyst even said, "Apple has peaked under the leadership of CEO Tim Cook."

But another analyst suggested that a single positive data point could spark a rally.

One of the most likely silver linings to Apple's June quarter earnings is iPad sales - CEO Tim Cook essentially said so during the last earnings call.

"In the June quarter, we expect to see our best iPad revenue compare in over two years," Cook said during his remarks.

"We continue to be very optimistic on the iPad business. And as I had said in my remarks, we believe we're going to have the best compare for iPad revenue this quarter that we have had in quite some time. And so we'll report back in July on that one," Cook said.

Well, it's July - and smart eyes will be on that iPad number. It's hard to determine what Cook means by "best compare," especially since he did warn that iPad sales would be down from the 10.2 million Apple reported it sold last quarter.

The iPad is a bit of a canary in Apple's gold mine. Before iPhone and Mac sales started dropping, iPad sales declined for eight consecutive quarters year-over-year.

And earlier this year, some analysts questioned whether Cook and his team perhaps had lost the thread, and raised the possibility that he has been misjudging Apple's business.

If iPad sales don't post what is clearly the "best compare in over years," it would be a very strong sign that Cook might not know what's going wrong with Apple.

Last quarter, Apple reported $4.41 billion in iPad revenue, and in its June quarter last year, it reported $4.53 billion.