Bill Nygren, one of the top fund managers of the past decade, says he’s been bargain-hunting in the wake of oil’s big decline.

“Given the recent selloff, this is the area to be opportunistic in,” Nygren recently told CNBC Pro. He picked up shares of Chesapeake Energy amid the oil free fall. “This is mostly a play on a changed company,” Nygren said. “There’s still a taint on the stock from prior management days, which they don’t deserve.”

Chesapeake is involved in the production of both oil and natural gas, which has also taken a hit this year. “This has been the momentum trade of the year, and there’s an awful lot of speculation in where the price action is,” Nygren said of the energy price declines. As for Chesapeake, he says, “There’s new management in share buyback mode and a very shareholder-oriented board. Basically everything they can control is pointed in the right direction.”

Chesapeake (CHK) gets a 90% score from Validea.com’s Joseph Piotroski-based model. Other oil and gas stocks that rate highly using John P. Reese’s Guru Strategies include ConocoPhillips (COP) and Statoil ASA (STO).