Not being a European basketball aficionado, my first exposure to Nick Calathes came in this year's preseason, when he was still tender on defense and turnover-prone on offense. My first impression was that he talented, but overreaching - trying to thread ambitious passes against all-too-capable NBA defenders and usually failing. It's been a long adjustment period for Nick, but with every game, he is turning more and more critics (including this one) into fans.
Unlike, say, Courtney Lee, who acclimated quite quickly to his new team's style, Nick Calathes had two barriers to overcome to make himself a legitimate rotation player. He first had to adjust to a new league and its high caliber talent and competitiveness. He then had to learn the Grizzly way: the no-flash, no-flair, workmanlike style that has made the current team so successful.
The coaching staff has done it's part to utilize Calathes' skills: playing him off the ball with Mike Conley, sending Miller in as an offensive go-to, and matching him up against smaller guards that he can out-stretch and pester on the dribble. In a February game against the Knicks, Calathes was brought in as a defensive substitute on the last possession of a game. That was a big moment in itself.
These days, Calathes fits the Grizzlies like a confortable pair of jeans. The 7 game crucible as a starter helped him solidify his offensive boundaries (and shine within them, averaging 14.7 points and 4.9 assists in those games), but where Calathes has surprised and delighted is in his defense. He's shown flashes of brilliance in one-on-one situations and as a team defender, whether it's shutting down John Wall, intercepting a high-low pass, or swiping the ball from a big with his back to the basket. Calathes lurks as well as anyone on the team, and yet never seems to be outside of his recovery zone. (Check out Kevin Yeung's piece here for a more in-depth breakdown.)
On a team loaded with top tier defenders, Calathes won't challenge anyone for the throne. But you can see he's absorbed lessons from Mike Conley's quick hands, Tayshaun Prince's long arms, and Tony Allen's reckless abandon. He's becoming a defense-first player on a defense-first team. (Not that he's regressing on offense, though - his assist numbers are consistently the best thing on his stat sheet.)
This is how Calathes has made himself valuable, maybe essential in a playoff rotation. If Jon Leuer provides spacing, Mike Miller provides offense, and James Johnson provides havoc, Nick Calathes provides disruptive defense and reliable ballhandling. No more, no less. His shot attempts are down, his assist numbers are up, and his turnover ratio is among the league-best since the All Star break. He's not a team leader in any category, but he's exactly what you want in a backup point guard, something Memphis has been searching for for years.