I'm not sure how Newcastle playing a game in the future has any links to their injuries now. I'm not sure if their extra games this season has a huge amount to do with their injuries either in all honesty. Come the end of the season they'd have only ended up playing 5 matches more than last season.
Sometimes **** just happens and when it does, it often spirals. You get a few injuries and as a result the other players have to play more, meaning they're more likely to pick up injuries. Rinse and repeat. There were times when Howe could have used his squad players a bit more but when things aren't going well it can be difficult to rest your better players unless you really trust the ones coming in. One of our Geordies commented on Howe needing to give Hall some games now but given how few minutes he's been given in a season where you've had so many injuries, it's pretty evident that Howe thinks he's rubbish.