True or false: Assuming that Duncan defends Shaq, the biggest single mismatch in the two starting lineups is Carmelo vs. Peja
I think it depends on how you define biggest mismatch.
If you're saying how much better one player is than his opposite, I think Peja and Carmelo are close. Carmelo might have a slight edge, but I don't think 2004 Peja (#4 in MVP voting who led the Webber-less Kings to a 55-27 record) is that much below 2013 Carmelo (#3 in MVP voting who led the NYK to a 54-28 record). They each won the first round of the playoffs and lost in the second round. Their scoring stats that regular season:
Peja: 24.2ppg on 48.0% / 43.3% / 92.7% shooting (62.4 TS%)
Carmelo: 28.7ppg on 44.9% / 37.9% / 84.8% shooting (56.0% TS)
The beauty of Peja is that he's so efficient and doesn't require the ball in his hands to be effective. I will have no issue if Peja scores less points than Carmelo in this series. The more shots Carmelo takes, at his level of efficiency, is a plus for the Utah Jazz when you compare it to the offensive efficiency Utah will generate. You could momentarily ignore Carmelo's poor 2013 postseason efficiency and go to the extremes in pretending Carmelo will have the most prolific scoring playoff series that he's ever had in his career* and it STILL wouldn't be very strong compared to what Utah will produce on offense.
There's a reason why you and I both drafted players like Peja and Manu ahead of Carmelo. Is Carmelo a more talented player than each of them and maybe even considered a "mismatch" in that sense? Will he score more points than each of them? Sure. But Carmelo has been presented with those types of mismatches in 90% of the games he's played in his career and he has never shown an ability to attack it in a way that leads to consistently efficient and winning basketball. Peja and Manu have both exceeded Carmelo in that area.
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*The nominees for those series would be:
2009 WCS: 30.0ppg on 49.1 FG%
2010 WC1: 30.7ppg on 46.4 FG%
Carmelo's actual 2013 playoff stats: 28.8ppg on 40.6 FG%