The bull market is in the later innings, and active managers must now step up to the plate, Nuveen Asset Management's Bob Doll said Thursday.
"In the early stages of a bull market when breadth is broad and everything goes up, it doesn't matter. You've just got to be there, so passive is fine," Nuveen's chief equity strategist told CNBC's "Squawk Box."
"Later in the bull market, when the market narrows, all of a sudden security selection is critical."
With the easy money in the rear-view window, Doll shared where he is looking for value — and where he is trimming his portfolio.
Nuveen is taking money off the table in the health-care sector and is now essentially neutral weighted, Doll said. Health stocks don't tend to do well in an election year, and share prices are looking a little expensive, he said.