The fund run by Bill Gross, which dropped more than 3 percent on Tuesday alone, plunged to last in its peer category so far this year, according to Lipper data on Wednesday.

Gross' $2.1 billion Janus Henderson Global Unconstrained Bond Fund is now down 6 percent this year, the research service's data showed.

Gross, once considered the "Bond King" of Wall Street, co-founded Newport Beach, California-based Pacific Investment Management Co in 1971 but left abruptly in 2014 and moved over to Janus.

Treasuries had their best day in more than seven years on Tuesday, but Gross has been bearish on U.S. government bonds and other sovereign debt.

In January, he told Bloomberg News that he had gone short - betting against - U.S. Treasuries as well as German and UK bonds.

In an interview in March, he said he expected 10-year Treasury yields to rise to 3 percent - they did earlier this month - and stay there. But yields fell, and were trading at 2.86 percent on Wednesday.

In the same month, Gross wrote in an investment outlook note that bond markets were like "a hibernating bear awakening" from a bull market driven by "lower inflation and excessive central bank accommodation."

Todd Rosenbluth, director of mutual fund research at New York-based CFRA Research, said investors look to bond funds for capital preservation and income generation.

"When a fund fails to deliver it can catch investors off guard," he said. "When Gross left Pimco assets failed to follow him. Unrewarded risk-taking fails to result in inflows."

Calls and emails to Janus Henderson were not returned.