A fierce strike 19 minutes from time by James Collins saw the Hatters secure three points on an afternoon when the tepid hosts produced a worrying offensive performance against combative and well-organised visitors.
Barnsley's best chance to equalise fell to substitute Dominik Frieser, but he headed wide at the far post as he spurned the chance of marking his league debut with a maiden goal.
Struber said: "I think for us, it is important we have players with a good dynamic from a physical side.
"They can help us. At the moment, we have enough skinny (small) players who have other advantages and strengths.
"I like and trust my players very well. But in some games, you need - from a physical side - some players that can help the team and save (hold) balls and bring advantages in set-piece moments.
"This is the situation.
"I hope for that (new signings next week). I think it is necessary."
On his side's display, he commented: "The opponents had a physical advantage and we had problems to find our way in the game, especially on the ball, we did not have the right bravery to break the lines.
"We had to play on the counter very quick and for that, we needed high discipline on the ball and we forgot in many situations today.
"The opponents found a good momentum and we had not so much control on the ball. It was the reason we lost this game and have to make better in the next games.
"We are realistic about what the players can bring and also in our team at the moment. We do not always have players on the field who have the right experience to play in the team from the physical side in the Championship.
"We need a good mix and discipline on the ball. The opponents only played long balls and with the pressing triggers to win balls in the opponents half, we had no chance. It was only a fight for second balls.
"This is another game style and we have to handle that in a better and more successful direction. Today, we had some problems.
"I am very disappointed. With the goal, we had not the right power to clear the ball. They were lucky with the shot and we were unlucky with our best chance with Frieser."
Struber confirmed that Clark Oduor missed the game with a groin issue. He expects him to be fit again in 'ten to 14 days.'
Aapo Halme also missed out with a facial injury sustained in a training session while on international duty with Finland.