The relegated Teesside club started the campaign among the favourites to earn promotion to the Premier League following a summer of substantial investment in the transfer market.
Results, however, have been mixed and Monk takes his side to south London sitting eighth in the table, five points adrift of the play-off places.
“You have seen it week after week as the results come in just how competitive this league is,” said the Riverside chief.
“There will be a lot more ups and downs, but the margin for error becomes less and less as the season goes on so we have to capitalise. It is in our hands and we have to build up some momentum now.”
The festive period, of course, is always a good time to hit form due to the number of fixtures played in a short period.
Boro are on the road again next weekend at Sheffield Wednesday before signing off 2017 with back-to-back home games against Bolton Wanderers and Aston Villa. New Year’s Day then brings a trip to Preston North End.
A repeat today, therefore, of Boro’s last trip to The Den in 2014 – a 5-1 triumph – would be most welcome.
“Every ground has a different atmosphere, but that is not the focus,” said Monk when asked about one of English football’s most intimidating arenas. “If we show that same desire and work both sides of the game as well it doesn’t matter where we go, we can beat anyone.
“I think they have had a solid first half to the season, which I expected. They are an organised side with a good work ethic. They will look at their home games, backed by their crowd, for points so it will be difficult.”