Gallen's challenge to players on Portsmouth peripheryÂ

The Blues assistant manager wants to see the likes of Louis Dennis, David Wheeler and Andre Green make an impact when called upon during  the upcoming busy period in the squad's schedule.

Kenny Jackett's side have 10 games in three competitions to negotiate between now and the turn of the year '“ including Saturday's postponed clash against Charlton, which has been rearranged for December 11.

During that timeframe, Jackett will need utilise his squad, giving those on the periphery an opportunity to impress. 

Dennis, Wheeler and Green all featured in the 3-2 Checkatrade Trophy win over Tottenham Hotspur on Tuesday.

Gallen is certain the trio will get more chances in the weeks ahead.

And Jackett's No2 has told them to be ready and show their worth when they do.

He said: '˜There are going to be some games at home when it's going to be tight and we need some game-changers. 

'˜I think the likes of Andre Green, Dave Wheeler and Louis Dennis, who all played on Tuesday night, can be all game-changers in the next few weeks.

'˜It's tough to change the starting line-up, it really is.

'˜From our point of view it's great because we have got a very settled team at the moment.

'˜But I can't see us going through the whole season with it not changing.

'˜Those lads need to be fit, ready, willing and enable to, when called up, be ready. 

'˜We're going to be looking for some game-changing moments from them in the games coming up.'