Microsoft shares sank almost 5% on Wednesday while the broader tech market rallied after analysts at UBS said the software company faces weakness, particularly in the cloud.
Keirstead pointed to concerns at Azure, Microsoft's cloud computing platform, and Office 365, the company's family of productivity software.
Microsoft provides year-over-year growth for Azure and other cloud services but doesn't give a dollar figure, nor does it specify how much of the growth comes just from Azure.
The Azure and other cloud services metric also includes, among other things, enterprise mobility and security, or EMS, tools that can be sold separately.
Cloud rival Google put together an estimate of Microsoft's Azure business, based on a leaked Microsoft document and some extrapolation of other market data.