Yepes and Martinez warn of Uruguay threat
Having progressed from Group C with a 100 per cent record, Colombia, even in the absence of talismanic striker Radamel Falcao, have been one of the most impressive sides at the tournament.
By contrast, their opponents in Rio de Janeiro on Saturday come into the game reeling from the news that star man Luis Suarez has been given a nine-match international ban for biting Italy's Giorgio Chiellini in their final group fixture on Tuesday.
Yepes, who sat out the 4-1 thrashing of Japan on the same day, underlined the importance of not taking their South American neighbours lightly.
"I believe that Uruguay are a difficult opponent and should be respected as we did with our group rivals," he said.
"It is a team that has more history than us, but we must prepare ourselves to face them in a good way because here there is no turning back."
Martinez, who started in a much-changed Colombia XI that took on Japan and scored twice in the second half to cap an impressive performance, lauded the support shown by the Colombians who have travelled to Brazil to back the team.
"The team has a huge motivation and I think that people have been an important part in everything that has happened," he said.
"We have felt an immense support, not only of Colombians but also of Brazilians.
"We have to go step by step, we cannot think of the quarters when we have an important match against Uruguay in the second round, which will define what this group has been looking for."