Six different chemical reduced mechanisms are used in a Large Eddy Simulation of a lean partially premixed swirled methane/air flame in order to investigate their capability to describe the flame structure and the species concentrations comprising the pollutant CO species. The mechanisms range from a two-step fitted mechanism to an analytical scheme composed by 13 species and 73 reactions. Following the classical approach, the performances of the mechanisms have been preliminary analyzed on laminar unstrained free flames. In addition, results for strained premixed counterflow flames have been discussed in order to evaluate their response to turbulence in a very simple way. This work demonstrates that the capability of a mechanism to describe three-dimensional complex turbulent premixed flames could be estimated on results for laminar one-dimensional unstrained and strained flames.