He may be starting to show signs of modest success but it is a long road back.
Since Gross' shocking exit from Pacific Investment Management last September, the firm he had helped launch and had built into a $2 trillion investment powerhouse has suffered big outflows of cash. Pimco's assets under management had dropped to $1.52 trillion as of June 30 from $1.92 trillion at the beginning of 2014 before infighting between Gross and CEO Mohamed El-Erian led to the departure of both in an eighth-month period.
But in recent months the exodus from the firm's flagship Pimco Total Return Fund has slowed from $11.6 billion in January to just $2.7 billion in May and $3 billion in net outflows in June. Figures for July showed a further decline of $2.5 billion, according to Pimco on Tuesday.
Its strong relative performance has helped to start to turn the tide.
The fund, which lost its crown as the world's largest bond fund in April to the $144.2 billion Vanguard Total Bond Market Index fund, is returning 1.56 percent so far this year, surpassing 96 percent of other funds in its intermediate-term peer category.
And Alina Lamy, senior analyst of markets research at Morningstar, said that the $47.4 billion Pimco Income Fund , which Ivascyn personally oversees, is also outperforming 96 percent of its peers in the multisector-bond category. The fund has attracted $8.7 billion since Gross' departure, though that is tiny against the $119.4 billion that has left Pimco Total Return in that time, according to Lamy.
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Some major clients are no longer considering redeeming money - or in bond market parlance they have removed Pimco from their "watchlists."
The $45.9 billion Teachers' Retirement System of the State of Illinois, with $2.4 billion invested through the firm, removed Pimco from its list in May, and the $2.4 billion Sonoma County Employees' Retirement Association did the same in June.
To be sure, the recovery at Pimco still has some way to go.
Big bond rivals BlackRock, Vanguard, DoubleLine and TCW have been beneficiaries - not only because of the departures of Gross and El-Erian, but also because of Pimco's weak performance in 2013 and 2014. Gross was there for most of that time and El-Erian for more than half of it.
Rivals and analysts say they are not yet convinced that Pimco has turned the corner.
"It is too early to make a judgment on Pimco," said Jeffrey Gundlach, the co-founder of DoubleLine, which oversees $76 billion in assets. "Less than one year is too early for any investment strategy. But I do think it would behoove them to clarify their investment process absent Bill Gross," he said referring to a sense that the firm is no longer transparent about the way it operates.
Gundlach's DoubleLine posted its 17th consecutive month of cash inflows in June and the Los Angeles-based firm has hired six Pimco employees since April 2014.
Todd Rosenbluth, head of exchange traded fund and mutual fund research at S&P Capital IQ, said Pimco "will need to continue to generate strong risk-adjusted returns for a more extended period of time for more investors to pay attention and to look to restart inflows."
Pimco faced another headache on Monday. The firm said it may face U.S. Securities and Exchange Commission civil charges over a smallish exchange-traded fund once managed by Gross.
Pimco, a unit of Germany's Allianz, said the SEC is looking at whether Pimco Total Return Active Exchange-Traded Fund properly valued small stakes in non-agency mortgage-backed securities it bought from its Feb. 29, 2012 inception to June 30, 2012, leading to inaccurate disclosures about the fund's performance.
Overcoming short-term pain
Gross' performance since joining Janus as a portfolio manager has been mixed.
The Janus Global Unconstrained Bond Fund, which he has been managing, posted cash withdrawals of $39.1 million in June, the second consecutive month of outflows for the portfolio.
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Gross declined to comment for this story through a Janus spokeswoman.
Pimco executives say that investors are noticing that the firm's outlook has improved markedly.
"People are excited because they clearly see that despite the short-term pain, in terms of the unwanted and negative media attention, the medium-term and long-term is better now than it was before," said Scott Mather, lead portfolio manager of the Pimco Total Return Fund.
Pimco executives rarely talk publicly about this renewed confidence. Ivascyn has appeared only once on CNBC since Gross' exit on September 26. In contrast, Gross has been on the business channel 10 times during the same period, according to CNBC.
Ivascyn said the Newport Beach, California-based Pimco still makes big, bold economic and investment calls but there's no burning desire to publicize them as Gross did.
"When you talk to clients and you talk to the media, at times, you reduce investment calls down to a sound bite or very simple views on the world," Ivascyn said.