After a fantastic run in 2014 when the stock gained 40%, Intel (NASDAQ:INTC) shares are down nearly 9% year-to-date. The shares are underperforming relative to the Philadelphia Semiconductor Index, which is up about 4% year-to-date, and compared to the Nasdaq composite, also up 4% for the year.

Here is my take on why the stock has not been a stellar performer this year. 

Fears of PC market weakness
For 2014, the company forecasted that its PC-related revenues should be "slightly down," as it sees flat PC-related units year-over-year, with modest average selling price declines. It also expects growth in excess of 15% year-over-year in its high-margin data center group.

I think that the company is likely to hit its data center group targets, but there was recently a report from BMO Capital Markets asserting that the notebook PC market was far weaker in February than its analysts had originally expected. In particular, February notebook shipments reportedly declined 17% month-over-month, which is far worse than the three-year average month-over-month drop of just 3%.

The fear for Intel shareholders is that PC sales might turn out to be worse than expected in 2015. Given that PC chip sales represent the majority of company revenue, a material shortfall here could have a meaningful impact on the both the top and bottom lines.

Will Intel warn?
Intel will typically issue a revenue and profit pre-announcement to investors ahead of its formal earnings report if the results come in materially lower than expectations. If Intel does not issue such a warning ahead of its April earnings report, then investors can likely assume that the quarter played out pretty much as expected.

While the lack of a warning would be welcome news to Intel stockholders, the next thing that could potentially have investors on edge is the possibility of weaker-than-expected guidance for the second quarter or even full year.

If Intel provides guidance in line with analyst consensus and reaffirms its full-year growth expectations, the stock might be pushed back into positive territory for the year. If not, then investors would have to consider the new guidance and assumptions, and the stock will be repriced based on those new numbers.

Keep watch for more analyst reports
I do not think that takeaways from a single analyst are enough to make an informed investment decision. But if multiple, reputable analysts are coming out with claims that their own, independent, channel checks signal unusually low PC demand, then caution going into the April earnings report could be warranted.

This is another reason why Intel needs to get into mobile
The fears surrounding the PC market, whether they turn out to be credible or not, underscore the need for Intel to become a major and profitable player in other high-volume client computing markets, namely tablets and smartphones.

The PC market may have stabilized, and if Intel management is right, it can grow at a low single-digit pace. However, the market for mobile processors is large and growing, and it is expected to continue growing for years to come. Having as much exposure as possible to large and healthy end markets is good, diminishing the risk from any weakness in PCs.