West Ham need to tread very carefully against Blackburn tonight.
The Hammers go into the game in a wretched run of form but there is no guarantee it will turn around against Rovers, who are second in the Championship.
They have taken 36 points from their 20 games thus far and sit just two points behind leaders Burnley.
They have a miserly defence that has only conceded 19 goals in 20 games, and boss David Moyes will have to go strong if the Hammers are to navigate the third round.
The Irons will also get a close-up look at summer target Ben Brereton Diaz, who has been in remarkable form for the Ewood Park side.
In total, he has scored nine goals and registered one assist in his 20 games for Blackburn this season, driving them forward and almost single-handedly accelerating their promotion push.
The Irons were interested in the summer and could be convinced to reignite their interest, particularly if he manages to score at the London Stadium tonight.
They are not a team to be taken lightly; West Ham could very easily slip up this evening if they underestimate the Championship outfit.