Boss Tony Pulis admits Rickie Lambert has suffered from West Brom's last-ditch deal to sign Salomon Rondon.
The striker moved from Liverpool for around £3 million in the summer to revive his career but has started just three Premier League games.
He has netted just once -- a penalty -- for the Baggies and is likely to be on the bench again for his Anfield return on Sunday.
Lambert left Merseyside because of a lack of first-team opportunities just a year after joining from Southampton. But he has been kept out of the Baggies side by £12m record buy Rondon.
Pulis said: "Rickie is knocking on my door all the time. He wants to play. It's difficult at times because I understand he wants to play.
"It's about trying to find the right formation and shape for the team and trying to get the balance right.
"In the back of our mind we were looking to bring him on against Tottenham [a 1-1 draw last Saturday] but we played so well, we were thinking 'who do we bring off?'
"We didn't think we would get Salomon right up to the last minute. Salomon was a real coup for us in lots of ways."
Meanwhile Pulis admits he is frustrated at the length of time it is taking Ben Foster to recover from a knee injury.
The keeper damaged his cruciate knee ligament in March but is yet to return after a setback in September.
He added: "I am a typical manager, you want your players fit as quickly as you can get them and when they're not fit you can get annoyed.
"You just want players fit but the medical people here do a good job."