Over the last four years? So 2012, 2011, 2010, and 2009? I'm assuming you aren't possibly counting 6 weeks worth of play as a full seasons worth of data?
I don't think think anyone who isn't practicing an extreme misuse of the English language can say that Paul decreased his OPS over the past four years vs the previous season. He increased his OPS in 2009 and again in 2010. I have no idea how a decrease in 2011 and 2012 (and six weeks in 2013) can be count as four years of regression by any stretch of the imagination.
He has decreased his OPS over the past two seasons, and I think there is no question whatsoever that he is on his very last legs, but let's not forgot that this is a man who drove us crazy with his streaks for the first 13 years of his career. Let's not pretend that his last two years weren't among the better seasons of his very successful career. Let's not forget that this is a man who used to be known for not showing up until May.