Bill Gross, the widely followed investor, admitted in his June Investment Outlook on Wednesday that his bet against the German Bund market was well timed but not profitable.

"My famous (infamous?) ‘Short of a lifetime’ trade on the German Bund market was well timed but not necessarily well executed," Gross, who runs the Janus Global Unconstrained Fund, wrote in his latest report to clients titled "Mr. Bleu."

Gross's Janus Global Unconstrained portfolio is down 0.40 percent so far this year, underperforming its peers by 1.88 percentage points and lagging 93 percent of its non-traditional bond category, according to Morningstar data on Tuesday.

Last month, Gross said he placed a wager against German bonds, tweeting on April 21 that German 10-year Bunds were "the short of a lifetime" and that the bet was better than the pound in 1993.

Gross was referring to investors George Soros and Stanley Druckenmiller, who made their names betting against the pound in 1992.