Actually the percentages seemed to go down with age, not up. Obviously it's just a calculator, not a perfect predictor. And yes, it's not zero, but my point is that it's not very high and injuries in football happen all the time. I won't avoid someone based solely on a 5% increase in major injury.
And while Holmes does have a history of history of acquiring injured players I still don't think a 5% increase is that much. Obviously it's one of many factors that need to be considered.