The British hedge fund’s paper gained 11.8p to close at 239.6p, although analysts were sceptical about the prospects of an offer.
BlackRock has pulled off large deals in the past, merging with Merrill Lynch Investment Management in 2006 and paying £8.6bn for Barclays Global Investors at the end of 2009. Commentators said it had the resources to buy Man Group but questioned the timing.
Numis analyst Gurjit Kambo said BlackRock would have to put at least 400p per share on the table.
He said: “BlackRock has the firepower to do it and they’re quite light in the hedge fund space because they’re focused on fixed income, but I think it’s unlikely at this point in time. Selling out when your core fund [AHL] is underperforming for cyclical reasons isn’t good.”
Another analyst said: “It’s not beyond the bounds of possibility, it’s just not that likely.”
Other than the £1.3bn cash on its balance sheet, Man Group has a renowned distribution network.
Man Group and BlackRock declined to comment.