Johan Bruyneel ruled out a departure from Astana by Spain's Contador, who won the Tour de France, Italy's Giro and Spain's Vuelta in little over a year.
The two will have to cooperate, he said.
"At the end of the day, the strongest rider will be supported, regardless of that person's name or what they've accomplished in the past," Bruyneel said in a press release.
And he left no doubt who was strongest now.
"Alberto has had a magnificent year and is currently the best professional cyclist in the world," Bruyneel said.
After leading Armstrong to seven Tour victories before his initial retirement in 2005, Bruyneel took Contador to victory in the 2007 Tour, and after Astana was denied entry this year, Contador won the Giro and Vuelta instead.
"Lance must prove that he has the physical ability to win big races," Bruyneel said.
When the 37-year-old Arm-strong announced his comeback and intention to compete for an eighth Tour title next season, it clashed with the ambitions of Contador, who insisted the leadership of Astana should be his.
The Spaniard let it be known he would leave if he was given a secondary role supporting Armstrong.
Bruyneel ruled that out on Thursday.
BANNED: Cyclist Riccardo Ricco was banned for two years by the Italian Olympic Committee after admitting to doping during the Tour de France.
Ricco tested positive for CERA, an advanced version of the blood booster EPO, after winning two stages of this year's Tour. He admitted taking the banned substance and was hoping for a reduced ban.
The Italian Olympic body, CONI, reduced the doping part of the ban by six months from the maximum two years.
But it also added six months because Ricco had gone to a physician who had already been banned for doping violations, Carlo Santuccione.