But while the Manchester United manager was playing a dangerous game in risking Wayne Rooney as the striker still struggles with a toe injury, his counterpart at Bayern was toying with altogether lower stakes.
"I bet you a big glass of beer," Guardiola grinned. "Rooney will play."
Moyes was forced to insist that he was not putting the England striker's World Cup hopes in jeopardy, but he did refuse to reveal the extent of the forward's injury. Rooney is expected to have a pain-killing injection in the toe on the day of the second leg.
That scenario evokes uncomfortable memories of what happened here at the Allianz Arena four years ago. Rooney injured his ankle in the first leg and was rushed back for the return fixture, only to be taken off after 55 minutes. The 28-year-old only played three more games that season and went on to have a disappointing World Cup.
"We think it's okay," Moyes said. "We wouldn't do anything medically wrong. We take advice from our doctors and the people who advise us. Everybody knows the character and the kind of player Wayne is. He is determined and if he is determined we would be mad not to [play him]."
When pushed on the injury, Moyes conceded that the club did know what the injury was, he was just unwilling to divulge the information with the gathered media in the Allianz Arena. "The doctors know," Moyes said.
What is not in doubt is that Rooney is the best chance for United to somehow get a goal in game in which they must score at least once, thanks to Bastian Schweinsteiger's away goal at Old Trafford last Tuesday.