Uralkali is likely to be removed from key stock indexes, and potentially delisted from stock exchanges entirely, after buying back another $2bn of stocks.
Uralkali announced on Friday has bought back 22% of its stock, for a value of some $2.0bn.
The move follows another buyback of around $1bn in June.
This leaves the deal has left the proportion of Uralkali shares in private hands at around 14%.
This reduction in the so-called "free float" could lead to Uralkali stocks being removed from key indexes, which are lists of stocks to be invested in by passive funds.
"The MSCI is likely to exclude URKA from the MSCI Russia index (and broader MSCI indexes)," warned VTB Capital warned.
Removal from the index would be bearish for equity prices, as the share would no longer be purchased by index-tracking funds.
VTB said the company's removal from the MSCI index could drive $30-35m of investment away from the stock.
Uralkali earlier warned that the reduction in free float could also trigger the company's removal from stock exchanges entirely.
China's sovereign wealth fund Chengdong Investment Corporation gave up a 12.5% share in the company in the most recent tender.
This leaves Uralkali largely in the hands of just two owners, the Russian fertilizer group Onexim and the private investment fund Onexim.
Markets have been eying the possibility that a merger between Uralchem and Uralkali is in the offing, with many seeing the delisting of the latter as the first step toward a tie-up.
Speculation about a merger gathered pace after a story carried by the Russian newspaper Vedomosti in June reported that a deal was being planned.
On Thursday Uralkali announced that its new head of overseas sales would be a former manager of fertilizer group Uralchem.
Oleg Petrov, an influential figure in the industry, resigned from his position as head of sales this week.
He will be replaced by Vladislav Lyan, formerly the deputy head of Uralchem's trading arm.
The position of Uralkali's head of sales is a key one in the global potash industry, as it entails running negotiations with the Chinese and Indian buying cartels.
The contracts agreed by Uralkali in these negotiations, as well as Chinese and Indian deals made by rival miner Belaruskali, and the North American potash exporting cartel Canpotex, are used as benchmarks for potash prices worldwide.
But Uralchem separately poured cold water on the idea of a tie up.
"By and large, there is no sense in a merger with Uralkali," Uralchem chief executive Dmitry Konyaev told reporters this week.
"It's a miner, while we are more chemists. They mine ore, our business is in gas processing. There is no significant synergy and logic in such a merger."
Uralkali shares in London were down 2.2% at $14.42 per global depositary receipts in late deals.
By William Clarke