The Scottish international returned to the starting line-up in midweek as Boro drew 0-0 away at Burnley, helping them to their first clean sheet since the middle of December.
The draw was only the fourth point Tony Mowbray's side have picked up this calendar year though, after losing six of their previous eight Championship outings.
Despite this poor run of form, which has seen Boro drop from third to sixth since their win over Blackpool at the end of December, McManus is confident that they can turn it around.
Speaking to the official club website, the 30-year-old said: "Every game between now and the end of the season is a massive game.
"But look at the quality we have got all over the pitch - we have nothing to fear."
Middlesbrough will look for only their second win the in the league in 2013 when they face Millwall at the Riverside Stadium on Saturday.