The fifth seeded Indo-Russian pair lost 3-6, 7-5, 3-10 to eighth seeded Romanian-American combination in one hour and 48 minutes at the Rod Laver Arena.
Paes was chasing a rare feat of winning two Grand Slam titles in the same tournament for the second time in his career but fell at the final hurdle. In the 1999 Wimbledon, he had won both the men's doubles (with Mahesh Bhupathi) and mixed doubles (Lisa Raymond) titles.
Yesterday, Paes had won the men's doubles title with Czech Radek Stepanek to complete a career Grand Slam. It was Paes' fourth Australian Open mixed doubles final, having won two and lost two. Overall, Paes has six mixed doubles titles with the French Open trophy missing from his Slam cabinet.
The combination of Tecau's strong serve and Mattek's stunning and powerful groundstrokes, proved too hot to handle for Paes and Vesnina.
Mattek hit some breathtaking winners, specially with her crushing forehand while Tecau hardly erred on his serve. Mattek and Tecau made a strong start to the match as they broke Paes and Vesnina in the second game to take the lead. Mattek returned well and played aggressively. One of her lobs and then a winner by Tecau earned them three breakpoints straightaway. They broke Paes' serve when the Indian fired a backhand to net.
Paes and Vesnina broke back immediately but Vesnina could not hold serve and they trailed 1-3, which became 1-4 when Tecau held his own in the next game. Paes finally held his serve, albeit after saving three breakpoints when Vesnina hit a volley winner on Tecau's return.
But there was nothing to worry their rivals as they had a comfortable lead and Tecau served out the set with ease when Vesnina hit a backhand to net. An early break of Vesnina's serve and easy hold by Tecau again put them up 2-0 and the eighth seeded duo led 4-2 at one stage.
However, a seven-minute break due to drizzle changed the complexion of the match. Perhaps the rhythm of Tecau and Mattek got disturbed and they began to commit a lot of unforced errors.
Mattek was broken in the eighth game and the scores were level. Vesnina served impressively in the ninth game to lead 5-4.
The pair broke Vesnina for the second time to take the second set and force a match tie-breaker. The momentum shifted yet again in favour of Mattek and Tecau following the amazing first point.
Mattek ran down the court on her right, just avoided colliding with an umpire but succeeded in hitting a stunning winner.
From there, Mattek and Tecau dominated the proceedings, not letting the hard work go into the drain.