Cricket's governing body has justified its decision to run a full trial of the "super-sub" rule in the one-day game despite heavy criticism.
Super-sub Plunkett took 3-51 in England's win over Pakistan
Inzamam-ul-Haq was the latest captain to hit out after Pakistan lost their first match under the rule to England.
The sub has to be named before the toss favouring the side calling correctly.
"The reason for the length of the trial was so that every team would get a chance to try it out in different conditions," said an ICC spokesman.
"In different conditions, the decision at the toss changes and tactics are different."
The trial will run until the end of March, before being reviewed by the International Cricket Council's cricket committee, headed by Sunil Gavaskar.
England's super-sub Liam Plunkett came into the side for Kevin Pietersen and took 3-51 on debut during Saturday's 42-run victory.
Pietersen had earlier hit 56 after England won the toss and chose to bat first.
By contrast, Pakistan did not have a chance to use their sub, spinner Arshad Khan.
If they had named a batsman in the role, won the toss and taken strike, they would have risked being a bowler short later in the match.
"The super-sub advantage lies with the team that wins the toss," said Inzamam.
"Had we won the toss we could have utilised our super-sub by bowling second time."
Rival captain Marcus Trescothick concurred, saying: "Winning the toss is the key to it.
"I think if you ask players around the world they would have teams naming their super-sub after the toss."
The concerns were expressed at the ICC captains meeting in Sydney in October and several international skippers have spoken out since.
The ICC cricket committee must decide in April whether the same rules will apply for an important next 12 months of one-day cricket, including the 2007 World Cup in the West Indies.
They could alter the plan, perhaps allowing the nomination of the substitute after the toss, or do away with the rule completely.
WHAT STARS SAY ABOUT SUPER-SUBS
Australia captain Ricky Ponting:
"To be able to name your sub after the toss would work better for everybody.
"'In its present form I'd probably say scrap it because the team that loses the toss can quite often be stuck without having that other option, so it's almost 12 against 11."
England's Andrew Strauss:
"It makes selection meetings pretty difficult.
"I would have thought with who to sub and who not to ... when to super-sub and when to take power plays, it makes things more complicated for the captain."
India captain Rahul Dravid:
"It's going to take some time before people move away from the norm and try out different things with the super-sub rule.
"But for the time being captains prefer batting on winning the toss."
New Zealand's stand-in captain Daniel Vettori:
"I understand how much influence there is from the toss and that's probably a little unfair."
Pakistan coach Bob Woolmer:
"I am actually not a great fan of it. I think it is loaded in favour of one side because you have to name your super-sub before the toss," he told Reuters in Lahore.
"I think both sides should be allowed to name their super-sub after toss."
South Africa captain Graeme Smith:
"The way it works at the moment is unfair and favours the side winning the toss far too much.
"If they want to keep a system involving 12 players then maybe both teams could name their respective 12th men after the toss when you know whether you're batting or bowling."