• Jair da Costa for Herrera's Internazionale: worked incredibly hard, but the defense + architect Suárez + golden boy Mazzola received most of the plaudits.
• Alberigo Evani for Sacchi's Milan: quality player but perpetually in the shadow of not just the GOATs, but Colombo/Donadoni on the flanks as well. Ditto Marco Simone.
• Gianluca Pessotto for Lippi's Juventus: went about his business without a lot of fanfare, most of the adulation was reserved for others.
• Claudio Makelélé for the Galáctico period, obviously: ushered out of the clubs by Pérez and many supporters foolishly reckoned he would be easily replaced.
Tempted to include Clodoaldo for 1970 Brazil: energetic presence behind his more illustrious counterparts, mostly an afterthought in the grand scheme of things. That being said practically any balancing-act midfielder would be overlooked in the company of Pelé, Gérson, Jairzinho, Tostão, Rivelino.
Maybe Keylor Navas for contemporary Madrid as he was the unfortunate victim of internal politicking despite saving their bacon many a time over the years, but he was well liked by a ton of fans and received a lot of individual awards/nominations (like 4 x FIFPro Squad member), so I'm not sure.
P.S. When you think about it, certain positions/characteristics/personalities are fundamentally conducive to unsung hero categorization — like water carriers or understated conduits or multi-purpose grafters or fullbacks that don't make significant statistical contributions. Hard to be truly remarkable or memorable in a lot of system-based roles along those lines.
), Furino, Brady.