Pakistan have not quite hit the panic button yet, but in adding Wahab Riaz to their World Cup squad two years after his last ODI and a year after Mickey Arthur seemingly signalled the end of the pacer's career, they have indicated growing alarm at the steep decline in their bowling performances.

On Monday, chief selector Inzamam-ul-Haq announced Wahab's surprise return, as well as the slightly less surprising additions of Mohammad Amir and Asif Ali, to Pakistan's 15-man squad for the World Cup. Junaid Khan, Faheem Ashraf and Abid Ali are the players culled from the provisional squad announced a month ago.

Why Wahab?

Wahab's last ODI appearance came as far back as on June 4, 2017, in the group stage game against India in the Champions Trophy, when Pakistan suffered a heavy defeat. He wasn't a part of the playing XI for Pakistan in their run to the trophy following that reversal.

He has played 17 List A games since then, taking 27 wickets at an average of 28.40 with an economy rate of 5.18. Ten of those wickets have come in five games this year, at an average of 20.70 and economy of 4.60, in Khyber Pakhtunkhwa's title run in the Pakistan Cup 50-over tournament.

More than those numbers, it seems to have been Wahab's ability to generate reverse swing - and Pakistan's poor form with the ball in England - that has swayed the selectors' opinion.

"Whatever you plan, you keep the room to review it as well," Inzamam said in Lahore. "I don't compromise on the team's requirements. If he (Wahab) wasn't originally picked in the squad, it didn't mean that he had been discarded forever.

"I understand he wasn't close to the 23 probables named for the World Cup, but no one is in the squad without a reason. The rationale behind bringing him back is his ability to reverse swing the ball. Nobody expected the pitches in the UK to be flat even in the early season there (during the recent ODI series against England). So we have realised that and reviewed our selection.

"We need to have bowlers who are good with the old ball and can defy the conditions and also have experience under their belt. Wahab has played in Tests recently and he was dropped on the basis of his form. But he did well in domestic cricket," explained Inzamam. "But it was the requirement of the team and the conditions there in England, which have changed drastically.

"Bringing him in doesn't reflect any panic, but it's a decision purely based on the requirement."

The comeback of Amir

Amir didn't - or couldn't - take part in any of the ODIs against England. He missed four of the five games with chickenpox but such has been the sense of worry following Pakistan's bowling in the series, it was almost certain that Amir's experience would see him return.

Pakistan conceded 373 for 3, 359 for 4 (in 44.5 overs), 341 for 7 (in 49.3 overs), and 351 for 9 across the four completed games. Mickey Arthur, the coach, pointed to the fielding lapses as the team's biggest concern after the series, but added that "our bowling has been average at best."

That has come on the back of a longer-term slip in bowling form, paralleling Amir's own dip since the Champions Trophy two years ago. In his last ten ODI appearances, Amir has picked up just two wickets at an unflattering average of 148.50, though he has usually kept things tight. In 14 ODIs since the final of the Champions Trophy, his economy rate has been an excellent 4.58, though if games against Zimbabwe and Hong Kong are taken out, it goes up to 5.28.

"If you analyse the series, if the Pakistan bowlers were punished, so were the England bowlers," Inzamam said. "So whatever the conditions, we need experienced bowlers, and Amir is very much ahead of every bowler we have. He was originally never discarded either, but we kept him with the team for the England series."

On the two pacers who were left out, Inzamam said, "Junaid and Faheem are dropped but that doesn't mean they are not good. But we think players like Amir and Wahab are more suitable for these conditions, which is why we have preferred them."

Pakistan did utilise the 30 days the teams had been given - April 23 to May 23 - to make changes. They had named a 17-man squad for the England series and also carried Mohammad Hafeez while he was still recovering from injury. Hafeez missed the initial games but played the last two ODIs, scoring 59 in the first of them.

Pakistan are, however, missing a reserve wicketkeeper behind captain Sarfaraz Ahmed, but Inzamam confirmed that Mohammad Rizwan would stay on in England and fill in in case of an injury.

"I see my team at No. 1," Inzamam said. "I am sure all teams are working hard for the World Cup, but I think Pakistan have the capability to win the World Cup."

Umar Farooq is ESPNcricinfo's Pakistan correspondent