Was selling Jaap Stam Fergie's biggest mistake?

Silvestre was fine as a left back and only performed well in central defense when Rio or Stam were mopping up his deficiencies.
For me, he was a player that for everything he did well (which was a lot to be fair-he had a lot of good attributes) there was a number of horrendous errors that followed. I never felt the team was safe with him around. I wish that treble team had been reinforced sooner, and with elite players, not squad level types.
 
Appointing Moyes was by galaxies Fergie’s most catastrophic decision, a decision which nowhere near recovering from almost a decade later, but dispatching Stam is a distant second.
 
Generally brilliant to adapt as the game moved on. His reluctance however to start paying agent fees when he personally felt they were getting out of control felt like a personal crusade…and one he labelled as no value in the market. He stopped chasing quality focusing instead on either lesser players and/or players with potential. It was a marked shift from signing the likes of Hazard, Aguero, Silva and instead ending up with Young, Valencia, Owen, Jones, Smalling.