Albion face Norwich at The Hawthorns on Saturday following back-to-back defeats in the space of five days to Newcastle and Manchester City.
With matches against Cardiff and Hull to follow, and then the busy festive period, Clarke knows this is a vital time for the Baggies to collect points, particularly after falling behind his targets.
"This is a key period for everybody (at the club)," said Clarke.
"We've had some really good performances, but haven't picked up the points we had to.
"Now we're going into a period where we've lost a couple, and that can always happen.
"When you're in a good moment you have to pick up the points, so now we're a little behind where we wanted to be which we have to address that over the next few games, starting Saturday.
"This time of year - December, January - you know after that period whether you will be fighting at the bottom or trying to chase those at the top.
"So that's what we have to do over the next few games, define where our season is going to be."
Clarke refused to concede that at this stage of the season the clash with Norwich had become a 'must-win' encounter given the form of both clubs.
Clarke added: "You can't define any game at this stage of the season. There are too many points to play for, but that's not to say it's not an important game.
"I'm sure the fans are expecting us to beat Norwich. We managed to do it last year, and this season we have to do the same.
"It was a difficult home game with them last year. We turned a 1-0 deficit into a 2-1 victory, which was good for us at the time.
"Then we went down there at the end of the season when Norwich were still fighting for Premier League survival, and they turned us over 4-0, so that's still fresh in the mind."
The Canaries, however, are going through their own crisis that has placed manager Chris Hughton under severe pressure and made him the favourite as next for the sack.
Norwich face Albion following a run of five successive away defeats, conceding 22 goals - albeit playing Arsenal, Manchester United, Manchester City, Newcastle and Liverpool.
Clarke believes Hughton deserves credit for what he has achieved with City so far, but will be all too aware the scrutiny he is under at present comes with the job.
"They're a good footballing team, always 100 per cent committed, always play for their manager, so we're expecting a difficult game," added Clarke.
"For me, I think Chris has done a terrific job, but the way the game is now - you see the number of sackings in recent weeks - it's a high-pressure business.
"We know when we sit in the hot seat that is what can happen to you.
"The short-termism of the game means you could be the next one under pressure, which we all expect.
"So Chris is aware of the job and its perils, but he has a good team and a good squad of players that always play well for him."
Midfielder Youssouf Mulumbu returns from a one-match ban, although centre-back Jonas Olsson is suspended for one game after collecting five yellow cards.