Costa has been struggling with an ankle injury picked up ahead of the win against Nottingham Forest a fortnight ago, while Mason’s last action was at Barnsley on January 31st due to a troublesome hernia problem.
Lambert has revealed that Costa was close to a return against Leeds but was still struggling when he tried to up the tempo in the final preparation.
“The other day we thought he had a good chance of being fit for Leeds when he raised the tempo, but that’s when he felt it,” said the Head Coach.
“The scan came back and showed there was a bit of inflammation there.
“We have to treat him accordingly.
“He’s tried to come back, he’s been out there trying.
“I certainly hope he plays again this season, with the season he’s had as well. "He’s been a massive part of what’s happened. So we’ll see what happens with the doctors and what they say.
"With a bit of luck he might be available for Saturday (against Blackburn), but that’s pre-empting it a few days before. Will he be fit? We’ll have to wait and see, but hopefully.”
Mason had made a fine start to the season before initially picking up an injury, but is now back in training and hoping to be involved soon.
Lambert added: “Joe’s had a really frustrating season, stop-start, stop-start.
“He’s got to have a season where he’s sustainable for 39, 40 games.
“Most players have to have that in their make-up.
“You can see he’s got great ability, it’s just keeping him fit to perform.
“The last week or so he’s been training and gradually building it up.
“We’ll see how he does this week. We’ve still got four games left so hopefully he’ll get some game time for the first team.”
