The high-flying Baggies face a run of six Premier League games in 31 days as they bid to maintain a run of form that has lifted them up to fifth in the table.
The former Liverpool and Chelsea assistant has used 21 players so far this season but has told his squad that everyone will have to play their part in the coming weeks.
He also sent a message to those players who have not featured regularly so far this campaign, revealing they will be an important asset in the season run-in when tiredness and fatigue can be an issue.
"This is when the squad will be tested," Clarke told the club's official website. "They will all be asked to step forward and make their contribution, that up until now, they have all made.
"We have got a good squad with good depth and over the coming weeks it will be used and tested to the maximum.
"There is a group that have played a third of the playing time or upwards and we're in good shape in terms of where we are fitness-wise and availability and having people ready to play.
"As we get to the latter stages of the season, hopefully we'll have players who are really fresh and they can keep the momentum going - that is the key of having a good squad."
Successive defeats against Swansea and Stoke have checked the Baggies' momentum in recent weeks after briefly going as high as third in the table following a 4-2 win at Sunderland on November 24.
Clarke though insists morale remains high in the camp and admits he would have gladly taken their current points haul of 26 had it been offered to him in August.
"I think the spirit at the club should be high at the moment and I said that to the players after the game on Saturday," he added.
"We were disappointed to lose but all I said was that they should be pleased with their efforts given where we are in the league.
"If at this stage in the season you'd have said that we'd have 26 points and we'd be level on points with Chelsea and Tottenham, towards the top of the league, they would have grabbed that.
"I've tried to tell the players that we're not in a bad place and we have to remain positive. In football you can lose games and we could lose the next game but we're still not in a bad position.
"There's no way we can allow negative thoughts to come into our heads."