1998: Duncan's rookie year, Michael Jordan wins his last le
1999: No one hurt, le
2000: Duncan hurt, Shaq was at his peak
2001-2002: Shaq was too good here and Spurs were re-tooling their roster and core
2003: No one hurt, le
2004: Duncan hurt
2005: No one hurt, le
2006: No one really hurt, barely get eliminated
2007: No one hurt, le.
2008: Manu hurt, Bowen hurt
2009: Manu hurt, Tony hurt
2010: Manu hurt, Tony hurt, Duncan hurt
2011: Manu hurt
2012: Fixed games 3-6 vs OKC, over a dozen allowed goaltends by Ibaka plus many, many other very questionable calls in OKC's favor
2013: Manu hurt, Tony hurt, nearly beat LeBron's super team anyway
2014: Pretty much no one hurt and look what happens. Another le
Let's not pretend like Ibaka is a superstar (only missed 2 games AT San Antonio, aka we likely won regardless) or that LeBron missing a few minutes in a game that turned out to be a blowout, followed by two more blowout losses even with him, was making a big difference.
Spurs have been constantly dealing with injuries that derail and hamper seasons. More than every other team with le aspirations. If you're using it as an excuse, then it can Just as easily be used as an excuse to suggest the Duncan Spurs could have had the most les since Russell's Celtics.
Playing the "what if" works more in SA's favor due to how often they've had to deal with injuries.