ESPN - Asia's five teams are all home from Russia, but January's 2019 Asian Cup already looms large on the horizon.

Here's a look at lessons all the AFC nations learned from the 2018 World Cup and what needs to be done in the coming weeks and months.

South Korea

Despite the stunning 2-0 win against Germany, South Korea's World Cup was a disappointment. There were some positives with the Taeguk Warriors, however.

First and foremost, the team have their No. 1 for the Asian Cup and perhaps years to come. Cho Hyun-woo would have been in contention for the goalkeeper of the tournament had Korea played an extra game or two. Kim Young-gwon also was another bright spot, looking back to his old self in central defence, and Son Heung-min impressed, though he tried to do too much. With injured players such as Kim Min-jae, Kwon Chang-hoon and Kim Jin-su fit and raring to go, South Korea will be carrying greater quality into January's tournament in the United Arab Emirates.

The Asian Cup is a tournament that South Korea has not always taken as seriously as it deserves. That is changing, and the KFA is keen to sort out the coaching situation as soon as possible -- Shin Tae-yong's future is uncertain,and the football association is looking at other options with some big international names being floated.

Much depends on whether stars Son and Ki Sung-yueng are available. The Tottenham ace might have other priorities, and Ki, who has just joined Newcastle United, has hinted at international retirement. With those two and the injured players returning, Korea have a real chance.

Iran

With Carlos Queiroz in charge, Iran will be the team to beat in the U.A.E. This is a team that pushed Portugal and Spain all the way in Russia. Four points are often enough at the World Cup, but unfortunately not for Iran in Russia.

Sardar Azmoun presents a problem heading into the tournament. The 23-year-old is one of the top strikers in Asia, but after Russia, Azmoun announced his retirement from the national team because the abuse he received on social media affected the health of his mother. All sensible Iran fans will hope the decision is reversed.

Team Melli's defensive-minded style might have (almost) worked at the World Cup, but that needs to change a little in Asia when Iraq, Vietnam and Yemen are not going to dominate Iran to the same extent. Fortunately, Queiroz's team showed in qualification that defeating Asian teams is not a major hurdle for them. At the moment, with Queiroz in place and the tournament taking place next door, Iran are surely favourites.

Japan

The only Asian team to survive the group stage made it a better tournament than anybody had expected, with the Samurai Blue unlucky not to make a first quarterfinal appearance. There is still the issue of the coaching situation, with the Japan FA now looking for a new man to replace Akira Nishino.

There is something of a changing of the guard with the retirements of Keisuke Honda and Makoto Hasebe. The former was becoming a bit-part player anyway, but Hasebe was a lynchpin in midfield, and his experience, composure and quiet charisma will be missed. The likes of Takashi Inui, Gaku Shibasaki and Yuya Osaka, however, showed that Japan have a new generation ready to take charge.

Goalkeeper Eiji Kawashima was erratic, and it might be time for the 35-year-old to step down and the much younger Kosuke Nakamura to make the step up.



Australia

Group C was always going to be tough with France, Peru and Denmark all ranked well above Australia, according to FIFA. The narrow defeat against France offered encouragement, the draw with Denmark was the one game the Socceroos should have won but didn't, and their World Cup ended with a whimper and defeat to Peru.

At least the Socceroos knew that a new coach is coming in Graham Arnold. Arnold struggled in charge of the team during the 2007 Asian Cup but has impressed with Sydney FC.

Arnold is first going to have to end the debate over Tim Cahill -- there were massive calls for the 38-year-old to come off the bench in all three games, but he did so just against Peru. It is surely time for the legend's international career to end, but the new coach might have to be the one that ends it.

Arnold has obviously developed as a coach since 2007, but his forays into Asian club football have not always been impressive. He needs a good showing in the U.A.E., or pressure might start to build quickly on the manager.

The World Cup showed that Australia has a solid team, though one that lacks quality in the final third. If the coach can concoct an attacking threat, it won't be easy to prize the trophy out of Aussie hands.

Saudi Arabia

After the opening 5-0 defeat against Russia, it was not looking good for coach Juan Antonio Pizzi. There were rumours that he was close to the sack, but the improvement in a 1-0 Uruguay defeat and the 2-1 win over Egypt ensured that the tournament ended on a much better note than it began.

It also ensured that Pizzi will be in charge in January. The Argentine wants a progressive and proactive game but was forced to close up after the Russia game. He now has more time to spend with the team, more time to get them playing from the back, and there will be more confidence going into the Asian Cup against opposition that won't be quite as strong.

The midfield looks pretty much sorted. Abdullah Otayf and Salman Al-Faraj settled to international football fairly quickly. Salem Al Dawsari scored an unforgettable last-minute winner against Egypt, and Fahad Al Muwallad caused problems. Osama Hawsawi is unlikely to continue in central defence, and the goalkeeping position is an issue -- Pizzi used a different No. 1 in all three games -- and the team still lacks a striker.