Versatile players like Gabriel Obertan and Antonio Valencia are "invaluable", according to Reds boss Sir Alex.
The new arrivals were unveiled at a press conference at Carrington on Monday, where the United manager was quick to sing their praises.
"They're both very quick and play in wide positions, although they can also play through the middle," he said. "Players who can play in several positions are invaluable in the modern game.
"You saw the contribution John O’Shea made last season – we played him in three or four positions and he was excellent in every one.
"But we like wide players at this club and [Obertan and Valencia] give us two more avenues to explore."
Sir Alex revealed United had been keeping tabs on French sensation Obertan for four years.
"We’ve monitored Gabriel since he was 16 years of age and he was probably the most sought-after youngster in Europe. His form dipped a little last year, possibly due to an injury, but he’s regained that form and was fantastic against England U21s earlier this year. That reignited our interest in the boy."
Most of the questions at the press conference were directed at fellow new recruit Michael Owen, although Obertan did manage to get a few words in.
"To play even a few minutes on the pitch in every game would be great. I'll work hard while I'm here and we'll see what happens...
"I think it would be pretentious of me [to talk about making France's squad for 2010 World Cup] but I'll work hard to progress and improve."
Valencia, too, had little to answer, but the Ecuador international did insist he felt no pressure to step into Cristiano Ronaldo's vacant boots.
"When I had my first conversations with Manchester United it was never said that I was coming here to replace Cristiano.
"Obviously Cristiano did very well here and he's a good player. But I’m here to do my job and to do the things that I do well. I’m keen to do well, I have a desire to do well, and I don’t really make any comparisons between myself and Cristiano."