"There's clearly a debate about what the impact of Mr. Gross being added to the platform will be," said Jefferies analyst Daniel Fannon, who has a buy rating on the stock and a price target of $17—well above the $14.36 Janus closed at on Monday.
Gross announced he was leaving Pimco, the firm he helped found, in September amid claims that he was about to be fired. The group, owned by Allianz, has suffered huge outflows since then from its flagship Total Return Fund.
As for what inflows Gross will be able to bring to Janus, Fannon said that many investors may be taking a wait-and-see approach.
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"People are going to want to see how [Gross] does and make sure the infrastructure is there for him before they write checks," Fannon said.
But Gross may even have an impact beyond Janus' fixed income business because he has brought positive attention to the group, Fannon added.
Janus may begin to see Gross' influence in its fourth quarter, but his real effect will not be clear until next year, Fannon said. Still, the bond expert may not be able to bolster the company's bottom line, as its equities products have largely lagged behind their benchmarks recently.
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Short sellers covered their bets against Janus in the first days after the Gross announcement, but they have since gone back in, Markit analyst Simon Colvin said. With the 7 percent one-month increase, Janus now has 20.3 percent of its shares outstanding on loan.
Janus is the seventh most-shorted North America-traded stock reporting earnings this week, according to Markit.
Here's the full Markit list: