Sir Alex Ferguson has the belief his Manchester United squad can last the distance in the race for the Premiership.
United have established a six-point lead over reigning champions Chelsea after Ferguson rotated his squad over the holiday period.
Ferguson was delighted with how his fringe players responded to the challenge and feels it bodes well for the rest of the season.
"There's been a couple of tests for us and it's been unlike last season," Ferguson is quoted in the Daily Star Sunday.
"When we played Wigan and Everton we made five or six changes and we won those games comfortably.
"That's a good test. But the other thing which is vital is that these players are getting older, so they must be improving.
"They're good professionals and are training well. When they get the chance we hope they take it, which they did against Wigan and Everton.
"If you look at our back four we have got Wes Brown, Mikael Silvestre, Gaby Heinze and Patrice Evra. Very experienced, capable defenders competing at left-back.
"I can play Wes at right-back or in the centre and I can play Mikael there, so the back four's okay.
"In midfield we have got reasonable cover with Darren Fletcher and John O'Shea.
"Then up front there's Henrik Larsson, Ole Solskjaer and Wayne Rooney, Cristiano Ronaldo, Louis Saha and Ryan Giggs.
"I believe in this squad. I'm happy with what I've got."