Cowen's Karl Ackerman dropped his rating on the Hamilton, Bermuda, chipmaker's stock to underperform from outperform. The analyst slashed his price target by a third to $18 a share.
Marvell's stock at last check lost 7% to $23.95.
While Marvell has attracted investor interest under the theory it is primed to capitalize on the 5G revolution, the move to 5G won't provide the bonanza for the semiconductor company that some have hoped for, Ackerman contends.
The majority of the 5G microcell stations slated to be rolled out in 2020 will happen in Japan and China, markets that are "dominated by network providers where Marvell commands very little share today," the Cowen analyst said.
As a result, Cowen foresees Marvell enjoying a considerably smaller bump from 5G infrastructure spending over the next couple of years than other market observers have anticipated.
Cowen's "most blue-sky bottom-up analysis" shows Marvell generating an "incremental" $450 million, or 25 cents a share, over the next eight quarters. That is "well below" the $850 million, or 80-cents-a-share, boost predicted by consensus models.
The investment bank and financial services firm also forecasts a decline in revenue in the storage sector, which currently accounts for 40% of Marvell's sales.
Ackerman is predicting a 3% decline in Marvell's storage sector revenue through 2022, as opposed to the 3% bump estimated by the company.
Marvell has had a bumpy ride upward in the past year, with lots of peaks and valleys on the chart.
The stock is up 40% in the past year. It touched a 52-week low below 18 early last February and a 52-week high near 29 in the middle of last month.
Bloomberg data show that of 28 analysts with ratings on Marvell stock, 21, or three-quarters, have buy ratings, 6 have holds, and Cowen is the lone sell-equivalent.