McDermott was critical of the defending as the Whites lost 3-2 at Huddersfield Town last Saturday and United have let in six goals in their last two away games to lose ground on the top teams in the Sky Bet championship.
At home recent wins over Bournemouth and Birmingham City have been more encouraging, however, and it is back to Elland Road this Saturday with the visit of Championship minnows Yeovil Town (3pm kick-off).
With Leeds expected to win there will be pressure to perform and McDermott is demanding a tougher mental approach after being unhappy that his team were guilty of missing chances at one end and guilty of careless defending at the other.
He said: “It is just so disappointing from my point of view. We were chasing the game at 2-2 and away from home we don’t need to do that. We didn’t defend one versus one situations properly.
“That could have been a different game. We seemed to lose our way after 15 minutes for whatever reason.
“When they scored we just lost our way but we hung in there. When we got back to 2-2 in the second half I thought there would only be one winner. And then we gave away an absolute shocking goal away for the third.
“We’ve got to learn how to win away from home and that’s the thing at the moment. Saturday was a really disappointing one.
“We played very well last week (against Birmingham) and on Saturday we could have scored four or five chances. We had four or five goalscoring opportunities that we didn’t take.
“You can’t give three goals away and expect to get a result.”
McDermott now switches his attention to Yeovil and after fielding unchanged sides for the last two games he may be tempted to bring in either of his two new signings, striker Dexter Blackstock who scored with his first touch as a substitute at Huddersfield after joining on loan from Nottingham Forest or Lithuanian international defender Marius Zaliukas who arrived on a free transfer after spending seven years with Scottish side Hearts.
Zaliukas has been brought in to add some experience and know-how to a young back line and impressed in a trial with the club before his signing to the end of the season was made permanent last Saturday.
Blackstock faces a fight to win a regular place up front, however, as it would be harsh to leave Smith out after scoring three goals in the last two games when finally given a chance to start.
McDermott also has to decide whether to continue with the 3-5-2 formation he devised for the last two games. It has had the desired effect of giving United a bigger goal threat and more width to their play, but they have not looked completely safe at the back.