Bremen lie 14th in the league at the midway stage of the season and have already been knocked out of the Champions League and the DFB-Pokal.
"We are in a difficult moment with Werder and we should not be talking about me at this time," he told the Kreiszeitung newspaper.
"I am needed here for our day-to-day work and it is my duty to concentrate on that.
"I cannot deal with anything else."
Mertesacker feels it is only right he concentrates on helping his current employers.
"Like I say, most of it does not even get through to me and I have told my agent that he should leave me in peace," added the 26-year-old, who still has 18 months left to run on his contract with Bremen.
"In certain situations, players should protect themselves by not losing track of the most important things in their job."