Having squeezed into the knockout rounds on goal difference, the Americans have taken full advantage of tournament...
Having squeezed into the knockout rounds on goal difference, the Americans have taken full advantage of tournament rules that allow teams to make up to six squad changes after the group stage.
Arena has used the regulation to bring in four players with more than 100 caps each -- Jozy Altidore, Clint Dempsey, Michael Bradley and Tim Howard.
With attacking midfielder Darlington Nagbe also drafted in, as well as goalkeeper Jesse Gonzalez, the American squad has a more familiar look to it from the experimental line-ups that faced Panama, Martinique and Nicaragua in the group stage.
"The players we're bringing now give us a little bit more experience, so I think it's a good mix with the group we had here already," Arena said.
"Group play was an opportunity for a lot of players to get a chance. Now as we enter the knockout phase of the tournament we've got to be ready to play each and every game - win and go on, lose and go home - so bringing in some experienced players, players with some quality, I think is just going to make our team better," he added.
The new additions should make Wednesday's quarter-final in Philadelphia a formality.
The US has only suffered one loss against El Salvador in the team's history, a lone defeat which occurred fully 25 years ago in February 1992.
The reward for the winner on Wednesday will be a semi-final against either 2014 World Cup quarter-finalists Costa Rica or Panama. Costa Rica and Panama also meet in the last eight on Wednesday.
In the other side of the draw, Jamaica face Canada in Glendale, Arizona on Thursday while holders Mexico face Honduras.
The final of the tournament takes place in Santa Clara on July 26.