Boro only managed a 3-3 draw at Plymouth Argyle last weekend and are sitting 12th in the Championship standings at the moment.
Michael Carrick’s side were in the playoffs last season, but they made a poor start to the ongoing campaign before picking up results.
Clarke admitted that Boro are getting better and are again looking like a good attacking side after their initial struggles.
However, he stressed that Boro are still looking defensively fragile and weak and have been shipping in goals left, right and centre.
He believes unless their defensive record sees an uptick, Middlesbrough will not be in the playoff hunt this time around.
Clarke said on What The EFL Podcast: “Middlesbrough are getting better going forward. They are getting better full stop and they are scoring more goals.
“They are a little bit weak and fragile at the back and that much was clear to see in this game.
“Van den Berg struggled a bit at right-back and the bottom line is that they have conceded the same number of goals as Sheffield Wednesday, who are having a stinker of a season at the bottom of the Championship.
“Unless that gets fixed, Boro won’t be in the playoff race this time around.”
Middlesbrough have a tough home game on Saturday when they will host Championship leaders Leicester City at the Riverside Stadium.
