After their surprise 2-0 win in Paraguay, the Chileans take on Bolivia in Santiago - and if they win and the leading duo Brazil and Paraguay draw in Recife, Marcelo Bielsa's side will take the lead in the South American qualifying zone.
Millar, who is expected to replace the banned Carlos Carmona, said: "We are playing a very tough match on Wednesday. We must win so the victory over Paraguay will have a more sweet taste. We beat a difficult team last Saturday, but the only important thing is winning, no matter the difference."
Bolivia coach Erwin Sanchez is expected to make six changes to the team that lost 1-0 to Venezuela at home last weekend. Midfielder Alex da Rosa believes this is the last chance Bolivia have to at least secure a place in the play-off tie against a CONCACAF nation.
"We will try to get the revenge after we lost to Venezuela. Each match is different and we hope so against Chile. We risk a lot," he said. Venezuela are very close to make history by getting into a FIFA World Cup for the first time, and they will be even closer if they can defeat Uruguay.
The Vinotinto have won three of their last four games and start only one point behind Uruguay, who occupy fifth spot - the play-off position. Oscar Tabarez's Uruguay, meanwhile, have to get over the 4-0 home defeat to Brazil quickly. Goalkeeper Sebastian Viera said: "I am fine, but I want revenge. We have not talked about the Brazil match with Tabarez."
Finally, in Medellin, Colombia take on rock-bottom Peru. The Cafeteros, who lost 1-0 in Argentina at the weekend, lie three points below the play-off position but their major target should be improvement, after winning only one of their last nine qualifiers, scoring six goals in the process.
Peru have lost their last five games and are virtually eliminated, despite a mathematical chance of playing in South Africa next year.