As the battle for corporate messaging clients heats up, investors and traders are beginning to choose whom they believe will be the winner.

Slack helped revolutionize the corporate messaging market and is still considered the market leader, in terms of features and maturity. In recent years, however, Microsoft Teams has gained ground, even surpassing Slack in overall users.

Despite Teams’ gains, Slack continues to be heavily used and has racked up contract after contract with some of the biggest names in tech. In spite of that, investors are worried about Slack’s long-term ability to successfully compete with Microsoft.

According to TheStreet, Goldman Sachs analyst Heather Bellini downgraded Slack from neutral to sell based on these concerns.

“While we continue to view Slack as a best-in-class team messaging offering that is favored by the technical community, we expect Microsoft Teams to continue to try and leverage its packaging within Office 365 to drive increased adoption, thus creating the potential for a more competitive environment,” wrote Bellini.

Another factor in the equation is Slack’s existing customer base. Because it appeals to small and medium-sized companies, Bellini believes it is more vulnerable to coronavirus-related economic issues. Despite downgrading Slack, she maintains her target price of $30.

Microsoft has a long history of entering a market with what is widely considered to be an inferior product, when compared with the market leader. Leveraging the power of their operating system and business-class software, however, Microsoft is usually able to make significant headway while improving their initial offering.

Only time will tell if Slack is able to succeed where so many other companies have fallen to the juggernaut from Redmond. If not, it may lend weight to Amazon’s rumored interest in buying the company.