Wednesday sees Spurs make their debut in this season's League Cup, with Championship leaders Forest visiting White Hart Lane.
The third-round tie represents Tottenham's third match in seven days, after a trip to Partizan in the UEFA Europa League on Thursday and a home Premier League encounter with West Brom on Sunday.
A 0-0 draw in Belgrade was followed up by a surprise 1-0 reverse to Alan Irvine's side, and Pochettino says his players need to be fully focused as their fixture list becomes more hectic.
"We need to be more prepared and more ready because the Premier League is strong and the Europa League is strong," he said.
"We need to change the mentality and make sure we are ready every time. You go to the stadium and you have to be able to compete and be strong because every game is different.
"We need to move the ball quicker, faster. West Brom played long balls and tried to win the second ball.
"We had a problem because we were always late to the second ball - we took a lot of time to get into the opposition's box. We need to be more aggressive in the last third of the pitch."
Pochettino made 10 changes for the Europa League fixture and, with a north London derby at Arsenal to come on Saturday, the Argentinian is likely to rotate his squad again on Wednesday.
"Our best starting team depends on each and every game - there is no doubt about that," Pochettino added.
"It's not an excuse. A bad performance on Sunday is not because of the changes. We have a very strong squad and we need to use our players - we have a lot of games ahead and after each match we analyse every player.
"At the moment the players are not in a position to play three games in one week."
