McKay dislocated his elbow during the 3-2 defeat to Shrewsbury on Saturday and is beginning an absence which could run into several weeks.
Fellow frontman Leon McKenzie is also out with his nagging knee injury so captain Andy Holt could again be asked to fill in up front. Former Coventry duo Marcus Hall and Kevin Thornton missed out at the weekend through illness but took part in Johnson`s first training session on Monday morning.
Johnson is hopeful of adding two loan signings to his squad in time for kick-off but defender Craig Hinton has had an injection in a long-standing knee injury and will be out for around a month.
Midfielder Ryan Gilligan has returned from his loan at Torquay a week early after suffering a family bereavement but cannot play until the Macclesfield game on March 12.
Source: PA
Source: PA