Is it not 4 years of Alfaro? And how much better can he get? What is his ceiling? Can he be a 4 win player? Cos thats what Realmuto is right now. Realmuto doesn't need to get better, he just needs to maintain his current level. Sure in two years hes gone or you have to pay him but you also have two years to find another ~4 win player to replace him.
C: Realmuto ~4 wins
1B: Hoskins ~3.5 wins
2B: Hernandez ~2 wins
3B: Franco ~1.5 wins
LF: McCutchern ~2.5 wins
CF: Herrera ~2 wins
RF: Harper ~5 wins
Total: 20.5 wins
or
C: Realmuto ~4 wins
1B: Hoskins ~3.5 wins
2B: Hernandez ~2 wins
3B: Machado ~5 wins
LF: McCutchern ~2.5 wins
CF: Herrera ~2 wins
RF: Williams ~1 win
Total: 20 wins
Both of those lineups look much nicer to me than the same but with Alfaros 1-2 wins included. Two to three additional wins may not seem like much but its so much easier to find those first couple of wins than the additional couple.