There were signs in year 4 that Perry was on the rise. One could argue that there are signs (specifically weight issues and explosiveness) that Lacy is going the other way.
I'd be more than comfortable seeing Ted give Lacy up to 4 per year. After that you have to start to weigh other options. The draft is loaded with backs that could replace his production and durability.
There were signs in the post season where he had just as many sacks as he had in the entire regular season. Throughout the regular season, he was non existent as a pass rusher and used primarily as a run defender due to his struggles on passing downs. In that season he also showed he couldn't stay on the field. while I'll openly admit he is our most important UFA, signing him to a massive extension is pretty scary. he's got just 1 season as a pro where he's looked like a capable starter and he's never played a full season in the NFL. He's shown to be as injury prone as any player we've got on the roster.
What signs did Eddie Lacy show last year that he was "going the other way"? Like I said earlier, no RB in the NFL had more broken tackles or yards after contact. He was also getting huge chunk runs as only 3 RBs had more 20 yarders. All this with just 14 touches a game and averaging more than 5 YPC. He was on pace to have his best season as a pro which is crazy considering Lacy is a usually a slow starter on the season. IMO, the biggest reason Lacy gets trashed around here is because he isn't and will never be LeVeon Bell or David Johnson. Some think RBs like that fall off trees are easily obtainable by all when reality is players like that don't come around very often. the idea that Eddie Lacy isn't' a starting caliber NFL RB anymore is nothing short of ridiculous (like stated above).
I'm not advocating for a massive deal and wouldn't at all be upset if we let Lacy walk due the contract he was able to get elsewhere or if he felt he had better opportunity elsewhere. My point is I just don't understand the negativity around him considering he was on pace to have the best season of his career last year before injury and he was doing it with fewer carries than he'd ever gotten in his 2 pro bowl caliber years.