Spurs' 1-0 loss against the Baggies was the second time they have been beaten in the league so far and leaves Pochettino's side ninth in the table after five games.
Tottenham are back at White Hart Lane on Wednesday when they face Nottingham Forest in the Capital One Cup and Pochettino wants his team to play with the same intensity against every opponent.
"We need to be more prepared and more ready because the Premier League is strong and the Europa League is strong," Pochettino 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."
Pochettino added: "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 to the side that started against Partizan Belgrade in the Europa League three days earlier.
The Argentine head coach is likely to make a number of alterations again for Wednesday's game against Forest but he insists rotation is no excuse for poor performances.
"Our best starting team depends on each and every game - there is no doubt about that," Pochettino said.
"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."
Tottenham need to bounce back quickly from last weekend's disappointment.
After Forest, they travel to Arsenal for the North London Derby on Saturday ahead of tough matches against in-form Southampton and Manchester City next month.
"We are in a good way," Pochettino said.
"When I arrived here I knew the situation - I knew that maybe there would be some ups and downs at the start of a new period.
"It's always different when you arrive at a new club with different players and you need time to get to know each other.
"I'm not worrying about the situation
I believe at the moment we need to have more points to reflect the table.
"It's the beginning of the season, it's not how we start it's how we finish.
"We are sure our team will improve not only in how we play but in the results over the next few weeks."
Source : PA
Source: PA