Thanks for running the numbers. I'm good with 10, because lower than that and you get the impression that almost nobody is any good.
In history there have been 569 position players as good or better than Brian Roberts (29 wins and change). Let's just say 600 position player become pros every year (20 per team for 30 teams, used to be less MLB teams but more MiLB teams), and pro baseball's been a thing for 150 years. So almost 100,000 pro players ever. Very roughly a 0.5% chance of becoming Brian Roberts the day you sign your first pro contract, on average. 10 WAR is more like 1.5%.
I'd still Pipp him or Alberto if Franklin Barreto could be had on reasonable terms and left alone to play six solid weeks to see what happens.
I still have fond memories of that time Ray Knight hit .600 for awhile as a new O.