"I have heard nothing about whether or not I will be playing, but being called back from Coventry came as a big surprise to me," said Grainger.
"In one sense it is excellent news because it is the chance to play Premiership football again. In another sense it is disappointing because I am leaving Coventry while they are in a good position.
"I have got my head down and got fit and I feel happier. I think Eric Black is pleased with me, but Coventry's rise up the table has had little to do with me.
"They would have got to where they are anyway because they are a good side. There is not much to read into being called back to Birmingham.
"They have got a lot of injury problems so you can see why they have done it."