MacDonald joined Leeds from Worcester Warriors in 2006
Head coach Neil Back has admitted Leeds Carnegie will miss prop Mike MacDonald during their most difficult period of the season.
The 123kg prop, 27, has flown to the United States for three internationals this month, meaning he will miss games with Bedford and Cornish Pirates.
"Mike goes away now and he will be missed," Back told BBC Radio Leeds.
"However that means there are opportunities for other players in the squad and they are ready for action."
Leeds maintained their unbeaten record in National League One by fighting back against Yorkshire rivals Doncaster Knights to win 28-13 on Saturday at Headingley.
The West Yorkshire outfit top the table by five points.
Back added: "There are things we need to look at, but we are still winning.
"The momentum is still there and so is the belief.
"We have two very tough games coming up but we will be ready for them.
BBC Radio Leeds will have full match commentary of Leeds Carnegie v Bedford Blues on 774 AM and DAB on Sunday from 1500 GMT.
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