"We were running into a market that had gotten so much fear at the end of last year, that earnings estimates came very far down, perhaps too far down," Timothy Lesko, partner at Granite Investment Advisors, said on Wednesday.
Lesko told CNBC's "Street Signs" that he expected a "snap back" from earnings revisions, but companies went further, reporting "much better" earnings and revenues. "It's been a nice run in the market, and maybe there's a little more room to go," he said.
Valuations are in the high teens now, but could trade north of 20 times earnings, he said.
"Maybe there's 10, 15% left" in the market's potential rise, Lesko projected, pointing to a "very, very pleasant" interest rate environment.
As investors consider the guidance given by analysts and companies, they will begin to see earnings going "significantly higher" in the future, he said. "And, in the long run, it's all about earnings."
"I think that probably could be one fly in the ointment of the story of looking ahead and seeing better times in the markets," he said.
Still, he maintained that those factors would not affect the "earnings run" in U.S. markets.
— CNBC's Fred Imbert contributed to this report.