It's not really "quite serious" because it's Brooks adding his own twist to the information.
McDonagh is "out indefinitely" because the Rangers dont' want to put a number on how many games he could miss, if any. The bit about the playoffs is just Brooks piling onto that and saying "and we don't know if he might misst he playoffs!!!!!!" which doesn't point to any kind of information of that nature, just stating the blatantly obvious that if the statement is "out indefinitely" then you dont' know how long that might be. Could be 1 game, could be zero games, could be the rest of the games, who knwos?
Yeah seems like he's sensationalizing. He's taking something blowing it up. It's like saying I paid more than 10,000 dollars for that care. I could have paid 1 million!