I don't understand this. Are you saying Davis is old?
Knile Davis was a 3rd round draft pick in 2013. He just turned 25 years old. Eddie Lacy turned 26 this last July. He is a year YOUNGER than Lacy
I'm not one to make bold predictions when it comes to situations like this, but another RB the Chiefs traded for from Baltimore after he fell out of favor during his first 3 years in the NFL in turned out to be quite the specimen in the early 2000s. My point is, weirder things have happened. To shrug this off as "nothing to see here" is really foolish IMO. Starks took over the RB duties practically last year. The RB situation has been a mess. Lacy has gotten fat and slow and just doesn't look the same as he did during his rookie season.
My opinion, Davis is an upgrade to Starks (who had knee surgery, out probably 4 weeks). Davis is younger and has an opportunity to flourish in an offense that historically has been very good. Worth a stash IMO