Rieder's comment came after data showed U.S. labor market suffered a sizable slowdown in the past few months.

The probability for a September move fell to about 40% Thursday.

The CME Group’s FedWatch tool shows a 66% chance that the Fed lowers its benchmark rate by 0.25 percentage point in September.

Rieder's comment came after data showed U.S. labor market suffered a sizable slowdown in the past few months.

The resignation of FOMC member Adriana Kugler also opens the door for a more dovish Fed shift.