Blades boss Chris Wilder was left frustrated having seen his side heavily defeated at the Riverside.
He remarked: "It's quite obvious what went wrong and when you go 2-0 from two set-pieces at a place like Middlesbrough, a top Championship, who have players from the Premier League, some of which are internationals, then you are going to be struggling.
"We made it a pretty comfortable night for them, although it wasn't second-half. Who knows what might happen if we'd got one or maybe two, we miss the best chances of the game by the way.
"I can't defend us not being organised from set plays and having people not prepared to do jobs."
Wilder added: "We're going to have to look at it closely because to those inside the stadium it would look like we don't work on set plays against, but we do and the players know their jobs.
"But if they switch off or don't have that desire then we are going to get royally punished and we've been punished.
"It's down to individuals and they've got jobs to do, we're going to have to look at everything, we might have to go to zone marking and change it up, but if I'm marking you, you aren't going to score because I'd have the desire and concentration for that ball not to go into the net, unfortunately we didn't have enough against a big powerful side.
"They've made their good deliveries, they've got that quality and had that desire to put the ball into the net.
"We're 2-0 down and then concede a third at the back stick and the game is done inside 25 minutes."