Conor Gallagher will struggle to win his place back in the West Brom side after their “incredible” result at Stamford Bridge.
Speaking exclusively to Football Insider, the former Albion and Arsenal striker tipped the 21-year-old to miss out against Southampton on Monday even though he has been “one of their best players” this season.
Gallagher was ineligible for Saturday’s 5-2 win over Chelsea, as he is currently on loan at The Hawthorns from the London club.
The attacking midfielder has been a rare share shining for the relegation-threatened side this season, with two goals and two assists to his name in 23 league appearances.
The Baggies welcome Southampton to the West Midlands on Monday and Gallagher will be once again available for selection.
However, Campbell is adamant Allardyce will snub Gallagher upon his return and name an unchanged side from the win at Chelsea.
“It is going to be difficult for Gallagher to get back into that side,” he told Football Insider. “100 per cent
“Look, Big Sam knows what he is doing and right now he has got a winning side.
“They were incredible against Chelsea and when you beat a team of that calibre, especially in the fashion they did, you have got to roll that team again if everyone is fit. Why would you not?
“Gallagher has been one of their best players this season but he did not play at Stamford Bridge. They beat his own team and this is football for you, it is ruthless.”