I'm not really worried, one way or another.
I think with four young arms (Velasquez, Eflin, Pivetta and De Los Santos) who can bring the heat, and a healthy Eickhoff, we're going to have excellent starting pitching (safety in numbers) and Robertson is the finishing touch to a deep bullpen (RH but great numbers against lefties).
So we didn't need to build a top five offensive juggernaut, just a solid offensive group that is at least average or better defensively (that alone will make a big difference with the young pitchers who all put up 3.80 or so FIPs last year).
Now you need a little luck, stay healthy, a bounce back year from Herrera or Altherr, one of Kingery/Franco/Knapp taking a step up - but nothing that is off the charts unlikely.
Adding Harper or Machado would be great, but if you have to buy Machado and he's gonna sulk with his megacontract - pass. And if Harper doesn't want to come here, same thing - it's one thing to pay a little more, but I don't think it's productive to bribe a player into going where he won't be happy, once he cashes the check, he'll still be unhappy.