It wasn't the first time arch-foes Iran and the U.S. have squared off in a sporting event in recent years.

But the men's volleyball match last week in Tehran — coming in the final days of tense international negotiations over Iran's nuclear capabilities — seemed to take on added significance.

The game itself seemed beyond history. Both anthems were played. Both flags hoisted. Iran then won 3-0 before some 12,000 cheering fans.

But on Iranian television, the U.S. anthem was muted.

In the words of one conservative Iranian analyst here, the anthem "brings bad memories" and would have been just a little too much. "We're not at the stage of playing the American anthem," he said.

No one here in Iran is pretending that a friendly volleyball game — or even a successfully concluded nuclear containment deal this week between Tehran and world powers (led by the U.S.) — will erase decades of enmity and mistrust.

Nor will it likely stop the bitter trade of accusations over terrorism, human rights violations and armed interventions.

But take a snapshot now, before the self-imposed deadline for a deal arrives on Tuesday, and it's clear Iran's place in the world has already shifted.

While not quite yet "in from the cold," it does seem to have at least a foot in the door.

You can see that in the re-establishment of direct (albeit limited) diplomatic ties with the U.K. last year, in the phone calls between the U.S. and Iranian presidents, and in the two countries essentially fighting on the same side in the battle against ISIS.

Fierce critics

You can also see that, of course, in the historic agreement in principle, agreed to back in April, on curbing Iran's nuclear program, a potential deal that has had its share of fierce critics here in the Middle East and on Capitol Hill.

Internally, Iran is also showing subtle signs of a country in the midst of important change.

Not long ago, "the nuclear issue was taboo, no one dared to say anything as far as the nuclear issue was concerned," said Sadegh Zibakalam, an outspoken Tehran University professor who was once sentenced to prison for writing a letter questioning the program's value.

Now, it is openly discussed, and Zibakalam's sentence was reduced to a fine.

IRAN-NUCLEAR/

The negotiators: Iranian Foreign Minister Javad Zarif (left), U.S. Secretary of State John Kerry and European Union High Representative Federica Mogherini in April, as the interim deal was announced. (REUTERS)

Iran was also visited recently by a European Union delegation and a flurry of foreign businessmen flying in to assess the opportunities should a final deal be signed.

A French hotel chain has already opened what the Financial Times described as the first Western-managed hotel in Tehran since the Islamic Revolution in 1979.

And Iranian officials are also speaking with new confidence about their place in the world should an international agreement come to pass.

An Iranian Foreign Ministry spokeswoman told CBC News that, in the event of a successful conclusion, Iran expects other countries, such as Canada, to fall in line and respect it.

Iran also expects to play a bigger role both regionally and internationally.

Reshape the Middle East

The end to Iran's isolation has the potential to reshape a Middle East power structure that has long depended on Shia Muslim Tehran shunted to the sidelines.

The possibility of its re-emergence onto the world stage has already made uneasy allies of Israel and Saudi Arabia, Iran's Sunni Muslim rival.

They are now joined by nervousness not only over how effective this nuclear containment might be, but over what any international détente with Iran would have on its influence.

Over time, a deal could well change the political calculus in the region, tilting it in Iran's direction. (It could also affect the dynamics of the international oil market.)

Without sanctions, and hooked up again to the world's economic mainline, Iran could once again grow its economy and perhaps become a regional economic heavyweight.

Unlike so many countries in the region, it is internally stable, with a young and highly educated middle class who are clearly anxious to reach out to the world.

At the most hopeful, a more confident, more economically buoyant Iran might begin to whittle away at some of the world's mistrust and even encourage more freedoms at home.

On the other hand, a more economically powerful Iran could also play a more strident role in the Middle East.

Obama Arab Summit

Seeking to reassure the Saudis and other Gulf State allies about Iran, President Barack Obama invited Saudi Crown Prince Mohammed bin Nayef bin Abdulaziz Al Saud, and other leaders to the White House in May. (The Associated Press)

Worth asking is what an emergent Iran would mean for the Syria conflict and the Iranian-backed Hezbollah's role in it. For the fight in Yemen. Or for the convulsive situation in neighbouring Iraq.

And what will it mean for the U.S.-Iran relationship long term?

"It is possible to forget and forgive past experiences, but …Iran cannot do it all on its own," says University of Tehran international affairs specialist Foad Izadi.

"It is possible to go beyond history, but it has to be a two-way street."

If nothing else, a deal with Iran this week would be a huge validation for diplomacy — sanctions, engagement and negotiation — to solve potentially deadly problems even among the most bitter enemies.

In a region where might has so often been deployed to resolve differences, a successful conclusion here would be hugely significant, though, in some quarters, not necessarily welcome, news.

The novelty of peacemaking may well be lost in the flurry of table-thumping by opponents, and in the many questions about what the world will look like with Iran once again on board.