Ken Arneson is still nervous, but I am not. The A's magic number is down to 4, with ten games remaining. The Angels have a magic number too: 19.
For the Angels to make the playoffs, they would have to win all 7 of their games against the A's and their three games with Texas. Meanwhile, the A's would have to lose two of three to the Mariners while losing all of those seven games to the Angels. It's not impossible, but it is so unlikely that I feel comfortable *not* worrying.
Baseball Prospectus' Posteason Odds Report says the A's chances of winning the division are 98.5%. Sounds good to me.