Striker Janssen is back in the spotlight with Harry Kane nursing an ankle injury, but the Dutchman faces a fight to rescue a miserable debut season at White Hart Lane.
His goal against Millwall last weekend was Janssen's first from open play since joining for £17.5million from AZ Alkmaar eight months ago and he failed to take his chance when Kane was out for seven weeks in the autumn.
Ten appearances in that period yielded only three goals for Janssen - all from the penalty spot - as Tottenham went five games without scoring from open play and six without a victory.
They can ill-afford a similar slump this time around, with Chelsea already 10 points clear at the top of the table and Pochettino accepts Janssen has endured a difficult opening season.
"It's true that in some period of the season his form was down," Pochettino said.
"He needed a wake-up [call] to be reminded that the possibility of playing could arrive.
"He is very young. He came from Holland. I'm happy with him and all the players, but I understand they are not happy with some situations.
"He is okay, he is motivated, confident - he is feeling a little bit of relief after his first goal from open play and that is important. I am happy in the way that he trained this week too."