D1 Capital Partners, run by Dan Sundheim, saw its equities book tumble 6% in March, making it one of the worst-performing hedge funds that month according to sources familiar with the matter. The steep decline came as the firm's largest equity bets moved against them during a volatile period for markets.

The worst-performing stock-picker designation highlights how concentrated positions can backfire during turbulent market conditions. Sundheim's firm appears to have struggled with timing and stock selection as its biggest investments faltered during March's market turbulence.

This performance underlines the risks concentrated portfolios carry, especially for hedge funds that rely on stock picking rather than diversified strategies. Investors may now question whether D1's concentrated approach can adapt to changing market dynamics as other funds with more diversified strategies fared better.