Morales injury is due to two factors, and both are equally responsible. Take away either one and he's not on the DL.
The first is when he made the final leap onto home plate he landed on one foot, instead of two. A lot of times you'll see a guy jump and land on both feet (think Jeter's Mr. November home run). Morales approached home plate like a hurdler approaches a gate.
The second is all his teammates were crowded - I mean really crowded - around home plate. As Morales made his final leap, it looks as if Eric Aybar, Izturis and Erving Santana to name a few are right there. Mid-leap, Santana appears to jump and pull Morales down. It's not beyond imagination to think Moralas landed with all of his weight on one leg right on top of someone else's foot, causing him to f*ck up his leg. It happens in the NBA all the time.
The lift off
Anaheim, we have a problem.
(His broken foot can be seen twisted in a weird angle here.)
Scocia was quoted in the paper saying something like 'obviously we'll have to change the way we celebrate at home plate.' Obviously. Having everyone keep back off the from plate until the batter arrives might be a good place start.