The central defender was earlier omitted from the England squad for their final Euro 2008 qualifier against Croatia at Wembley Stadium on Nov. 21.
"It was the right decision to leave him out of the England squad," Grant told reporters.
"I spoke with (England manager) Steve McClaren. I have been a national manager and if he was available I would be very happy for him to play but he's not fit yet.
"Maybe in two weeks he will be fit. And we need to take care of him. He always gave his body for Chelsea and the national team and now we need to take care of him because he's had a lot of injuries and I hope this is the last one."
Chelsea also confirmed that their Czech Republic goalkeeper Petr Cech will be sidelined for at least three weeks with a calf injury suffered in the Champions League at Schalke in midweek.
But England left back Ashley Cole will return from an ankle injury for Sunday's Premier League game at home to Everton.
"Ashley has trained three times and he's ok," said Grant. "He's available for the next games. But Cech has a bad injury like (Portuguese right back) Paulo Ferreira. In three or four weeks they will be available."
Cole, who was hurt on international duty against Estonia last month, is back in the England squad named on Friday after doctors decided he did not need an operation on his ankle.
Grant also suggested McClaren should pick in-form Frank Lampard in midfield against Croatia after leaving him out in recent matches.
"England can win without him but they can play better with him because he's a player that is very efficient and very good for the national team," he said.
"He's playing well for Chelsea after coming back from injury. He's hungry to play."