Is that why the Panthers were so eager to re-sign him
I honestly have no idea why he isn't resigned. For all I know, they made him an offer and he rejected it because he wanted more money. Or perhaps he was dead set on retiring and wasn't going to come back regardless. Either way, everyone was very high on his play last year. In addition to PFF having him as #3 LG (#5 Guard overall), and #1 FA guard, Rotoworld had this to say: "Wharton was quietly one of the best guards in the entire league last season, but the 33-year-old is hanging 'em up in hopes of enjoying a normal post-football life."
I'm not saying our guards this year are bad or even that Silatolu won't be as good/better than Wharton. I'm just saying Wharton was no slouch last year and played at a high level.