Ukraine captain Andriy Shevchenko gave his side a huge World Cup boost on Thursday, scoring as a second-half substitute in his first game after a month out with a knee injury.
Shevchenko, the 2004 European Player of the Year, featured for 30 minutes as Ukraine beat Luxembourg 3-0 in their final warm-up.
Coach Oleg Blokhin said it was too early to give Shevchenko a clean bill of health.
Ukraine open their Group H campaign on Wednesday against Spain in Leipzig and Blokhin said: "In a few days we can say how he is feeling."
The 29-year-old, one of the most feared strikers in world football, appeared to show no ill effects from the injury which forced him to miss friendlies against Costa Rica, Italy and Libya.
South Korea took preparations for their World Cup opener against Togo to a new level on Thursday, as coach Dick Advocaat ordered a closed-doors morning training session and swore his players to secrecy.
South Korea have never had a closed doors session since Advocaat took over at the end of September last year.
The Koreans face Togo on Tuesday, France five days later and what could be a crunch match with Switzerland on June 23.
No reasons were given by the Korean FA's representatives as to why the session was closed to reporters.
Spain midfielder Xavi says that he is now back to full fitness after missing five months of the season because of a serious knee injury.
"On a personal level I've noted a big improvement in the knee in the last couple of weeks and now I can say that it is perfect," the Barcelona playmaker told a news conference on Thursday.
"Before I had some pain in the tendon but now it's gone completely. All I needed was some match practice," he said.
Six Croatian players missed training on Thursday, with recuperation the watchword after the warm-up game against Spain.
Coach Zlatko Kranjcar conducted the lightest of work-outs following Wednesday's 2-1 defeat in Geneva.
Captain Niko Kovac and defender Josip Simunic received back treatment from a specialist in Munich, and Ivan Klasnic traveled to Berlin for non-soccer-related reasons.
Defender Igor Tudor nursed a slight thigh strain while midfielder Darijo Srna and forward Ivica Olic only did some stretching exercises.
Iranian left back Sattar Zare seriously injured his right knee in training on Thursday, while midfielder Ferydoon Zandi has not been able to shake off a fever caused by the flu.
Neither player may be able to play in the World Cup, coach Branko Ivankovic said after a practice session on Thursday.
"We'll see tomorrow how serious it is after an MRI," Ivankovic said.
Australia captain Mark Viduka was forced to sit out his team's practice session on Thursday after injuring his leg while warming up.
A team spokesman said Viduka had felt some tightness in his right calf but would be fine for Australia's first Group F match against Japan on Monday.
The Australians have been plagued by niggling injuries in the lead-up to the tournament and the sight of Viduka limping off at the heavily-guarded Otto-Meister stadium would have been a major concern to the camp.
Viduka had completed just two slow laps when he stopped.