Arsène Wenger is not enjoying his press conferences. Even his quips are not buying him headlines or breathing space. Life has become pretty oppressive for the Arsenal manager and it is because there is only one thing that anybody wants to ask him. "Why haven't you spent any money? Are you going to spend any money?" Spend, spend. Money, money. It is getting under his skin.

What has not helped is that Tottenham Hotspur, who Arsenal face in Sunday's north London derby at Emirates Stadium, have spent money. Lots of it, and on exciting and powerful players. Tottenham might be losing Gareth Bale to Real Madrid but they have attacked the summer transfer market to demonstrate ambition. Nobody knows how it will work out but they have had a proper go and their supporters can feel optimistic.

The mood at Arsenal contrasts sharply. It is edgy and fragile. The club only ever seem to be one defeat from crisis but lose on Sunday and it would be the stuff of nightmares, particularly if Wenger then has an uninspiring transfer deadline day on Monday. His latest targets are the attacking midfielders Julian Draxler and Kaká, of Schalke and Real Madrid respectively.

So far, he has spent zero pounds, despite his squad looking thin and the consensus that they need a world-class signing or signings to fire a title challenge. Wenger, though, will not be put under pressure. "We will not do anything stupid just for the sake of saying that we have done something," he said. "We do what makes sense or not. That is simple."

Tottenham think that this is going to be their year, the one in which they finally knock Arsenal off their perch. Not since 1995 and never in Wenger's 17 seasons at the club have Tottenham finished above them. But they believe that they are stronger this time, even without Bale, and they also know that they do not have much ground to make up. Tottenham were pipped by Arsenal to fourth place only on the final day of last season.

"That was painful because we thought we were a better team than Arsenal," Jan Vertonghen, the Tottenham defender, said. "I think we are getting stronger than last year. We've bought some very good players. It's good to have some freshness and competition, and the mood in training is very good. Everybody can feel it. It's a message to everybody in the top four that we want to be in there."

Vertonghen spoke of the physical power that Tottenham have added, in the shape of Paulinho, Etienne Capoue and Nacer Chadli, who are also no slouches on the ball; of greater options for tactical variation and a more clinical focus.

"At the start of last season," Vertonghen said, "we conceded late goals to drop points in our first two home games [against West Bromwich Albion and Norwich City]. I don't think that is going to happen again."

Wenger, though, has heard it all before. These are halcyon days for Tottenham in the league; fifth, fourth, fifth, fourth represents their most consistent level of top-flight achievement since the 1960s. But they always finish behind Arsenal.

Wenger was irritated to be asked last week about whether Tottenham's spending had intensified the competition for a top-four finish. "I hear that for 16 years now," he replied. But he was more calculated on Friday morning when he assessed another summer of transition for the Tottenham starting XI.

"In our job, there is always a technical risk when you buy more than three players because you unbalance a little bit the stability of your squad," Wenger said. "It's always difficult, when you bring so many players in, to predict how everybody will do."

Wenger suggested it was easier to predict a team's fortunes without their star player, a loss that he has suffered all too often in recent summers. Bale's world record move from Tottenham to Real will be announced shortly.

"It has a negative impact when you lose your best players, always," Wenger said. "Because you are perceived as well by your fans for a lack of ambition, and by the rest of the squad … they look for strength in their team. We have gone through that process consistently and it demands always a mental adjustment to keep your ambition alive. It's very, very difficult."

Wenger banged the drum for stability and he once again sought to remind everybody of the quality of his team, who have lost only once since 3 March. Chelsea, he noted, had begun last season as title contenders and yet they finished just two points ahead of Arsenal.

There was even a barb attached to the Lukas Podolski hamstring injury update – the forward could be out for more than 10 weeks and for him to recover full match fitness should take three months. "We have players who have quality and it is a shame that people only see it when they are injured," Wenger said.

He admitted that he had not intended to re-sign Mathieu Flamini as a free agent when the former Milan midfielder first returned to train with the club three weeks ago only for "circumstances" and the player's application to change his mind while Wenger also raised the outlandish prospect of a comeback for Nicklas Bendtner.

The striker has fallen so far from favour that he is training in solitary confinement but there have been 52,000 reasons each week over the summer for why he has not managed to agree to terms elsewhere. "The chances for him to leave now are very small," Wenger said. "If he does not leave and prepares well, and is fit, really fit, then I will use him."

Wenger returned to the subject of economics when he discussed the inflated summer market, which he said had been shaped by the vast resources of buying clubs and not the quality of the players. Real, he said, had been "very generous" with their fee for Bale.

And Arsenal? "We have financial potential, I wouldn't deny that," Wenger said. "But we will decide still to pay the right price."