Sunderland boss Steve Bruce admits the Christmas/New Year period will be decisive.
When the Premier League season resumes next weekend, there will be no more international interruptions until mid-February.
Bruce said: "It's been very stop-start so far because of the international breaks.
"It's quite incredible really - we've only played 11 games in three months up to now, and yet there could be 11 or 12 games in December and January.
"Those months around Christmas can be the defining time of the season, and yet the fixture list is piled high."