The Wales defender has been Tottenham's first-choice left-back for most of the calendar year so far after Rose's 2016-17 campaign was cut short by injury in January.
The England ace is due back in September, but it remains to be seen if he will win his spot back under Mauricio Pochettino, let alone even be at the club, after an explosive interview earlier this month in which he seemed to criticise Spurs' transfer and wage policy.
Should he leave, Keown isn't convinced that the 24-year-old has what it takes to replicate Rose's standard this season, suggesting Pochettino should bring in someone else in.
"They could do with spending some money on a left back and more pace in the wide areas," the Arsenal legend told The Daily Mail.
"Spurs have lost Kyle Walker to City and Danny Rose to injury.
"Those two were such a potent weapon last season. Kieran Trippier is capable of bombing down the right hand side but Ben Davies cannot replicate the job of Rose."
Keown might be a little harsh on the former Swansea City man, who has done a very decent job in defence since taking over from Rose, but it's true that Tottenham would improve by signing a better player.