New-Ozeki basho are almost always mediocre for the New Ozeki. This is because the between new promotion and the next basho are extremely busy with various social events, parties, interviews, publicity and the like that cut into keiko time, as well as the mental pressures and releases of becoming Ozeki. Once the promotion is achieved, the concentration required to clear the hurdle dissipates, and is replaced with Ozeki-debut jitters. Usually they're back to normal after the first basho.
First example, Chiyonofuji clinched Ozeki with a 14-1 yusho as a Sekiwake. His first Ozeki basho? He lost his first day and went on to finish 11-4. Akebono went 9-6 in his first Ozeki basho, as did Musashimaru. Asashoryu himself started strong, but crumbled in the second half, finishing 10-5.
Also, don't count Harumafuji out just yet. He lost the first two days of his Ozeki-clinching basho as well.
Josh Reyer
Swa sceal man don, žonne he ęt guše gengan ženceš longsumne lof, na ymb his lif cearaš. - The Beowulf Poet