After getting burned 2 years in a row, I'm not putting much stock in his "progress." Coaches and especially players put a positive spin on injuries/health, so you never know how bad it is till they're put on IR and you're like, whoah, didn't see that coming. All that matters is game day.
But I am curious about objective info on recovering from Achilles tendon surgery for athletes. In this
article, a surgeon reports that high-level athletes generally benefit from the surgery and can return to full, aggressive play in 6 months. (It's been 7 months since Merriman's surgery.) This
study from a couple years ago found that two-thirds of NFL players come back from an Achilles tendon rupture and those who do "find their performance significantly affected" (especially RBs and WRs). Merriman didn't rupture his tendon and there have been advances in the last couple years, but the study does suggest that the full post-surgery recovery time for an NFL player might be longer (11 months) than the generally accepted 4-6 months (again, that's for ruptures...partial tears have a shorter recovery time).
Interestingly, the study notes that NFL players coming back from Achilles surgery traditionally have followed an "overly conservative treatment protocol" that may have limited their full recovery. Newer research has pushed more, earlier weight-bearing activities and intensive strength training, so Merriman's recovery could be faster/stronger based on this revised rehab protocol.