Byron Buxton just got a promotion, but not to Double-A. He'll be facing better competition than that this fall.

Buxton is one of seven Twins prospects who have been invited to the Arizona Fall League, a six-week gathering of some of the best prospects from across minor-league baseball.

Buxton, batting .335 with 12 home runs and 52 stolen bases at two levels of Class A this year, will be joined on the Glendale Desert Dogs by outfielder Max Kepler, second baseman Eddie Rosario, and four pitchers from the Twins' organization: A.J. Achter, Zach Jones, Trevor May and Alex Meyer.

Meyer, widely considered the top pitching prospect in the Twins' system, recently returned to action at Class AA New Britain after missing more than a month with a sore shoulder.

The Fall League begins in early October and end in mid-November.

Meanwhile, if a tweet by Hall of Fame sportswriter Peter Gammons is correct, Josh Willingham is about to go through the week of uncertainly that Justin Morneau experienced two weeks ago. Willingham, batting .214 with 12 home runs during an injury-plagued season, has been placed on trade waivers by the Twins, Gammons reported via Twitter, meaning any team can claim the 34-year-old outfielder's contract, worth another $1.2 million this year and $7 million next year.

If a team claims Willingham, that team would have 48 hours to work out a trade with the Twins, who could also simply let the team have his contract with no compensation. If no team claims him, the Twins could trade him to any team. Players must be acquired by Saturday in order to be eligible for the postseason.

Amid all that, the Twins are taking on the Royals tonight, opening a three-game series in 90-degree heat. Both teams have cancelled batting practice today.

UPDATES: Don't expect to see Oswaldo Arcia for awhile. Manager Ron Gardenhire said before the game that Arcia still experiences sharp pain in his hand when he swings the bat, so the Twins will keep him out of the lineup for several days to let it heal. Gardenhire said the team has had to pry information out of Arcia, who wants to play through the injury, but it had become clear that it's affecting his play.

Arcia won't necessarily go on the disabled list, however, since rosters can expand on Saturday. Gardenhire said the Twins don't want to strip Rochester of another important player while they're in the heat of a pennant race -- the Red Wings are a half-game out of the wild card spot in the International League, and 3 1/2 games behind Pawtucket for the North Division title -- and they can probably get by with just two bench players until Saturday.

Joe Mauer was at Target Field today, and told Gardenhire he "feels decent," but it doesn't sound like his return from a concussion is going to happen for awhile, either. "He's getting better, but it's just going to take time," Gardenhire said. It's hard to imagine the Twins risking his condition in 90-degree weather here, or the 100-degree temps they'll face in Texas over the weekend, so figure Mauer to be at least 10 days from returning, at least as anything other than as a designated hitter.

Josh Willingham said he isn't aware that he's been put on waivers, not that a player normally would be, but he's not looking to move on. "I'm comfortable here," he said. Gardenhire said if he was a manager in a pennant race, a guy with Willingham's power would be appealing, despite the difficult season Willingham has had.

The Twins have changed their signs for this week's series, "and that scares me, since we didn't know them that well before," Gardenhire joked. But with Jamey Carroll on the Royals' bench, just three weeks removed from being on the Twins' bench, they had no choice. Would Carroll steal signs from his old team? "Absolutely," Gardenhire said. "He's on the other team. I wouldn't expect it any other way."

Here are tonight's lineups for the 7:10 p.m. start (in 90-degree temps):

ROYALS

Gordon LF
Bonifacio 3B
Hosmer 1B
Butler DH
Perez C
Lough RF
Getz 2B
Escobar SS
Dyson CF

Shields RHP

TWINS

Dozier 2B
Herrmann RF
Morneau 1B
Willingham LF
Doumit C
Colabello DH
Plouffe 3B
Thomas CF
Florimon SS

Correia RHP