Levi Mackin has been ruled out of York City's visit to Grimsby Town tonight and could be sidelined for anything up to three months subject to further examination. Former Wales under-21 international midfielder Mackin (below) limped out of the weekend defeat to Kidderminster Harriers with possible knee ligament damage and is currently awaiting further tests to determine the full extent of the problem. "It`s a bit blown up at the moment so we can`t tell what it is," Mackin told The Press. "At the time, I was really worried because my knee was making a weird clicking noise and I thought it might be a medial ligament injury, which I`ve had on the other leg in the past."I was gutted because it was 40 minutes into the new season and probably my first tackle but we don`t know what it is yet because there`s a lot of fluid so you can`t get a proper look at it."I`m keeping my fingers crossed and hoping that I`ve just jarred it," he continued. "I could hardly walk on Saturday and was on crutches but it`s a bit easier to stand on now."Manager Martin Foyle could decide to go with former Grimsby winger Peter Till in Mackin's absence, although Neil Barrett will also come into the equation after being left out at the weekend.However, ex-Altrincham centre-back Greg Young is again unlikely to be involved for the visitors, while fellow newcomer Duane Courtney will probably once more be named amongst their substitutes.The Mariners are definitely without Rob Atkinson (hernia), Charles Ademeno (hamstring) and Lewis Gobern (thigh), while Bradley Wood (ankle) and Nick Colgan (elbow) are both rated doubtful.