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Needham analyst Scott Berg says that while much of the Street will likely applaud Salesforce's (CRM) potential acquisition of Slack Technologies (WORK) because it could accelerate revenue growth over the long term, he's more cautious on what would be Salesforce's first big transaction outside of its customer-centric core platform of sales, marketing, and service.

The deal would be less sales synergistic than something in the middle office would have been, Berg tells investors in a research note.

Further, the acquisition, if completed, would push off additional margin expansion for Salesforce into fiscal 2023 at the earliest, "which does not counter the bear thesis," contends the analyst. Berg keeps a Hold rating on Salesforce saying he's "not enamored with this potential deal."