Keep in mind that without the injury Freddie may have been headed to an MVP year and that we were 1-5 without him and 5-5 with him.
Based on quick analysis of the new contracts and discounting 25% for Fred's age -- you are looking at $6M a year current value (top tier at $8-10M). Fred signed an extension for 4 years/$7.5M total in 2009 covering 09, 10, 11 and 12.
I would add 2 years and $15M to the existing contract--$10M up front and keep him through 2014. I think that is fair for everyone--takes care of Fred without killing us. His base is likely about $2M for this year so you are giving him $10M in cash up front and then paying him $2.5M in base in 2013, 2014 which is back up money.
End result, over six years he will make $22.5M - the first two of those were as a part-time starter and the third year he is a FT player but injury shortened. He likely has 3 years of good productivity left.