The Welsh captain has not played since the goalless draw against Estonia on September 8 after being injured on his return to Real Madrid. The absence of the 32-year-old for October's double-header deals a serious blow to Wales' qualification hopes for the 2022 World Cup in Qatar.
Page is confident Bale will be fit for November's closing two World Cup qualifiers against Belarus and Belgium but said: "You grade hamstring injuries from one to four and his is nearer the four.
"So it's quite a significant hamstring tear. We've been in close contact with him to see how it's progressing but this camp has come too soon for him. Originally it might have been progressing into November's camp, that's the significance of the injury. Thankfully he's recovering better than anticipated. We're pretty certain we'll have him for November."