Despite reaching the quarter-finals of the FA Cup, Millwall have lost their last five Championship matches, and seven of their last nine to fall away from the play-off places and slip to six points above the drop zone.
The nadir of that run arrived on Tuesday when they were humiliated 5-1 at home to a Peterborough side who hauled themselves off the foot of the table with the thumping win.
Now Millwall travel to take on Middlesbrough, who are still in the hunt for a top-six finish, but on a wretched run themselves after losing six of their last eight in the league.
"We have to draw a line under Tuesday," said Jackett, speaking to independent website NewsAtDen.co.uk.
"It is good this is a big game against a big club that is live on the television, and an opportunity for us to rediscover our league form, which has been poor while our FA Cup form has been good.
"The two have run almost in parallel to each other and to some degree that is frustrating, but it is what it is. The sooner we get ourselves out of it, the better.
"The only thing we can do about it is put on a good performance and win against Middlesbrough. That's what we are looking to do. We need a big response from all of us."
Jackett will be hoping veteran centre-back Danny Shittu is available after missing the last two games, initially with an ankle injury and then with flu.
With left-back Shane Lowry starting a three-match ban after he was sent off against Posh, Jackett already faces a defensive reshuffle.
Boro, meanwhile, are without striker Lukas Jutkiewicz and defender Stuart Parnaby after they sustained ankle and hamstring injuries in last weekend's 4-1 loss to Crystal Palace.
Mowbray knows, given Boro's poor form of late, a top-six finish is still comfortably within their grasp.
"We're fully aware the chasing pack are right on our heels now and the only way to stay in front of them is to win football matches," said Mowbray on the club's official website.