Juande Ramos admits chasing a trophy treble this season could damage Tottenham's hopes of continuing their Premier League revival.
Spurs are in the knockout stages of the UEFA Cup, the semi-final of the Carling Cup, and victory at Reading last night put them in the fourth round of the FA Cup, setting up a tie with Manchester United.
Ramos established himself as a cup specialist at Sevilla and it is two years since he has been knocked out of a competition - but he is wary of stretching his squad.
'This is the biggest concern,' said the Spurs head coach. 'We are making a great effort to win these games and the result is injuries, exhaustion and suspensions. It's very difficult to keep momentum.'
Reading boss Steve Coppell believes Spurs can end their nine-year trophy drought by lifting the FA Cup.
'They could win it, of course,' he said. 'Are they capable of winning six games? Yes. Are they capable of going to Old Trafford and winning? Yes.'
Ramos added: 'We're going to try but the next game is very difficult for us and we know just how tough it will be and we'll do everything possible to beat Manchester United.'
The third-round replay was never going to have the fireworks of the 6-4 or the 2-2 the last two times these sides met - but there were still plenty of chances at the Madejski Stadium.
Robbie Keane grabbed the only goal of the game, in the 15th minute, when he stabbed in after Younes Kaboul headed against the crossbar from Jermaine Jenas' corner.
Leroy Lita showed plenty of energy in Reading's attack but the closest the hosts came was when substitute Stephen Hunt volleyed against the crossbar. Steed Malbranque did the same for Spurs in injury-time.
Coppell rested half of his team but insisted: 'It was never our intention to have the cop out of `now we can concentrate on the league'. We wanted to go through.
'The prospect of playing Manchester United away is daunting but it is privilege, it's exciting and makes the hairs on the back on your neck tingle.
'The magic of the cup is still alive. You can get an awful lot of satisfaction and self-esteem - ask any of the clubs who win against the odds. Who cares if they are not going to win, they have fabulous day where they went against higher opposition.'
Chris Gunter, who made his Spurs debut, remains the only January signing for Ramos but the Spaniard is expected to have new faces in his squad soon.
Andrei Arshavin, the Zenit St Petersburg and Russia forward, has been linked, while Middlesbrough winger Stewart Downing has appeared to be edging towards a move to White Hart Lane.
'I've known him for two years, since we played against Middlesbrough in the UEFA Cup final,' Ramos said.
'He is a player I know well, I don't have to watch him.'