Analysts at Deutsche Bank estimate that Pimco, plagued by weak returns and capital outflows but determined to retain clients post Bill Gross' departure, could suffer a reduction inn assets under management of €210bn or a fall in assets equivalent to 20% over the next two years.
Deutsche Bank research argues that each €100bn (£78bn, $127bn) in outflows is equivalent to some 9% of assets under management (AUM), which brings down Pimco's parent firm, German insurer Allianz's earnings by some 2%.
Deutsche has also cut its price target on the insurer to €135, from €140, but maintained a hold position on the stock.
Allianz's stock was trading 0.99% lower to €128 at 14:53 CEST in Frankfurt.
Meanwhile, Bernstein Research sees asset outflows of between 10% and 30% and expects a "good deal" of Pimco clients to move to Janus Capital Management – Gross's new employer.
Morningstar has put all of Pimco's rated funds under review, including the iconic Total Return fund, which, despite its downbeat performance in 2014, remains the world's largest bond fund.
Credit Suisse has cut its rating on Allianz to neutral from outperform.
Bernstein analysts led by Thomas Seidl said: "We estimate that a drop in AUM of 10% would have a minor impact on Allianz fair value of 2%, while a 30% drop in AUM would hit the stock by around 13% according to our fundamental valuation mode."
Russel Kinnel, director of mutual fund research at Morningstar, said: "While it is not a shock to see Gross depart, it is a big surprise to see him leave so quickly and to a competitor."
Credit Suisse said it expects "uncertainty to linger until the market can get greater visibility on the ultimate loss of [assets under management] and also any impact on costs within Pimco as management seeks to compensate for the damage of the departure and founder."
Neil Dwane, chief investment officer, equity Europe, at Allianz, told CNBC that Gross's longer term track record and his "brand value" meant investors felt the "integrity of Pimco was very strong".
"His departure means they will recalibrate that, so the market's fears about outflows are simply a logical concern."
Pimco chief executive Doug Hodge has said that the Pimco Total Return fund, which was run by Gross, "does not define Pimco".
Hodge and Dan Ivascyn, who has assumed charge as Pimco chief investment officer, told Reuters earlier that they have spoken to clients about the new leadership.
Pimco has appointed Mark Kiesel, Scott Mather and Mihir Worah to run the $222bn Total Return fund.
Gross, 70, quit troubled Pimco on 26 September to join Janus.
Since the beginning of the year, investors have pulled out $25bn from the Total Return Fund and $6bn from the Pimco Unconstrained Bond Fund, according to Morningstar data as of end August.
Both were personally supervised by Gross, who also managed the Pimco Total Return ETF, the focus of a US SEC probe.
Gross co-founded Pimco in the 1960s.