Wales forward Gareth Bale is out of World Cup qualifiers against the Czech Republic and Estonia (AFP)
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."
Bale's eight-year stay in Spain has been dogged by injury and his regular absences in recent seasons have not gone down well with Real supporters.
"Gareth is a very special player and we know he will be missed," said Page.
"But we can't cry about it. We've got to get on with it and look at it in a positive frame of mind."
Juventus midfielder Aaron Ramsey, who missed this month's qualifiers, is named in a 28-man squad for the Czech Republic clash in Prague on October 8 and the trip to Estonia three days later.
The 30-year-old could take over the captaincy.
Wales are third in their World Cup qualifying group, level on points with the Czechs but nine points behind leaders Belgium.
The top team in each group qualifies for the World Cup, with second-placed teams going through to play-offs.
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