Celtic are set to make a move for a new defender before the transfer window shuts as Cameron Carter-Vickers, Maik Nawrocki and Stephen Welsh are ruled out for eight weeks.
Inured midfielder Reo Hatate will also be out until after the international break, meaning he will miss the first Old Firm game of the season at Ibrox on September 3.
Manager Brendan Rodgers revealed the news on Thursday as they prepare to host St Johnstone at Celtic Park on Saturday.
He said: “It’s disappointing for us in terms of Cameron Carter-Vickers, Maik Nawrocki and Stephen Welsh, will probably be about eight weeks.
“Stephen had an operation just the other day and he’s came through that well, the other two we hoped would be back sooner but the scans on them puts them at probably about eight weeks from now.
“Reo Hatate and Kobayashi will be back during the international break, Mikey Johnston and Oh will be back in training next week.
“Alistair Johnston is back, which is good news for us, he has trained well and will be available for the weekend.”
On looking for defensive reinforcements before the close of the window he said: “It something we have to look at, there’s no doubt that it’s an area that we are light on.
“When you are losing three players for that length of time and knowing the amount of games that we will have, and the importance of every game, then it is definitely something we have to look at.”
He also revealed they will be bringing some more quality in to bolster the squad in a few key position over the next week, saying: “We will do that before the end of the window. We are hoping to get that done over the coming days.
“We need to improve the squad, there is confirmation on any names at the minute, lots of names have been floated about, so as soon we sign anyone we will let you know.”
The Hoops will be looking to get back to winning ways against the Premiership’s bottom side after last weekend’s cup defeat to Kilmarnock.
The defeat was Rodgers’ first domestic cup defeat at Celtic after winning 24 out of 24 in his first spell in Glasgow.
“I think what’s important to understand, when you are trying to be successful, is that losing and failing in games is integral to becoming successful.
“It was a disappointing result for us, we didn’t do enough to win the game, but it’s also something you have to have at a club this size, you have to have that mental strength and that mental toughness to cope with disappointing results then be ready to go again.