While Pellegrini has been hugely impressed by Lampard's contribution, on and off the pitch, no decision has yet been made over the player's involvement beyond February.
However, City's Champions League fate is likely to influence Pellegrini's recommendation about Lampard to the City board.
With Yaya Toure due to be absent for up to five weeks in January and February as a result of Africa Cup of Nations commitments with Ivory Coast, Lampard's presence as cover during that period is assured. But if City lose in Rome next Wednesday and therefore go out of the Champions League and Europa League, they would be left to compete in just the FA Cup and Premier League in the second half of the season.
With Toure, Fernando, Fernandinho and James Milner already capable of playing central midfield, as well as the Argentine defender Martin Demichelis, the need for Lampard to remain at the Etihad Stadium beyond February would diminish should City have no European fixtures.
Lampard and the City hierarchy are also aware of the sensitivity of the arrangement with New York and the importance of the player being in the United States in time for the start of the MLS season, both for football and commercial reasons.
Claudio Reyna, New York City's director of football, admitted recently that, while he had no firm date set for Lampard's return to the States, "the plan is Frank will be in pre-season with New York City FC".
New York are expected to undertake some of their pre-season preparations in Manchester, at City's newly opened Etihad Campus training ground, in a move that would enable Lampard to spend some time working with his new teammates. However, neither City nor Lampard believe there is a need to commit to a decision on his future at this stage, with the aftermath of the trip to Rome next week likely to be the point when discussions begin in earnest.
City travel to Sunderland, the scene of defeat in each of the past four seasons.
Despite City cruising to victory at Southampton, Lampard admitted that the trip to Wearside would be difficult following Sunderland's 0-0 draw at home against Chelsea on Saturday.
3 things about Lampard
Top performer
Manuel Pellegrini has been hugely impressed by Lampard's contribution, on and off the pitch.
Goals keep coming
Lampard has scored five goals in 11 matches.
February deadline
No decision has been made over his involvement beyond February.