The playoff prediction algorithms are pretty much a joke. A team could have an awful April where half its team is injured, a mediocre May while they rehab, and be set and ready to go into June/July and be ranked near the bottom of the list. It only takes aggregate performance into account, which isn't much good as rosters change/improve, trades happen, and rookies come into their own. Basically, they're about as useful as fielding percentage.