DiClemente said Mayer — hired away from Google last summer to revive Yahoo — was able to assemble a solid team in her short tenure.
But the forecast on revenue was light, "particularly on display," he pointed out in a "Squawk Box" interview. "One of the bear cases on Yahoo is going to be that the number of impressions or number of ads sold ... is down. The number of ads sold was down 10 percent in the [fourth] quarter."
He also stressed mobile as an area for improvement. "They need to do a good job on mobile. Yahoo has got to be an app when I'm on my iPhone that I want to download."
DiClemente has a $22 price target on the stock, but said the upside case is much higher.
"You should see a velocity of new product announcements and accelerate throughout the year. Mail, Flickr. And those are the things we really need to see work. And that's where you get the escape velocity in the stock to the upside."
DiClemente said also he was surprised by the strength in search for the quarter. "Search really accelerated in terms of number of clicks. And to me, it's a positive indicator that they can really turn the dial on search monetization."
—By CNBC's Matthew J. Belvedere; Follow him on Twitter