Davis and Holland were both rather pedestrian last year and both were awful in the 2nd half. It's possibility they realize how fickle RP'ing is, accept their bodies may be failing them and know this is their last chance to cash in. If they continue the slide this year, they could be looking at 3 or 4 more years in the bigs, working off shorter contracts with lower AAV's.
It might look like this....17M + 4($6M) = $41M
Dave Cameron is predicting Davis gets 4 years, $68M and that Holland gets 3 years, $45M. Pencil in a final year for Davis at $5M and an extra 2 for Holland at $10M for comparison purposes.
If I'm in that position, I'm looking for guaranteed money all day long. I'd rather take the pay day and potentially leave $10-20M in career earnings on the table than take the risk that I'll remain healthy and effective....especially when dominant, deep bullpens are all the rage right now.