The Portuguese side were expected to register all three points against Cluj on matchday one and take an early step towards qualifying from a group which also includes Manchester United.
But a 2-0 defeat at the Estadio Municipal immediately placed them on the back foot and increased the need for a win in Istanbul.
Salvador knows, however, that very few teams win at Gala's intimidating Ali Sami Yen Spor Kompleksi, where they have lost just one of their last nine European fixtures.
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He told reporters: "Of course it's a very important game after the unexpected defeat to Cluj.
"We know what we must do to achieve our goal - which is obviously to win.
"However, we will encounter a difficult opponent as Galatasaray showed great quality against Manchester United (a 1-0 defeat).
"Our team must show a humble attitude and fight like warriors to get the three points."
Braga go into the game on the back of a morale-boosting domestic win on Friday when they saw off local rivals Vitoria Guimaraes 2-0 to consolidate third place behind Benfica and Porto.
Gala endured a miserable weekend after losing their Super Lig clash 2-0 to Orduspor to have their lead at the summit trimmed to a single point.
That match saw Hamit Altintop limp off although he is expected to be fit to start.
Central defender Tomas Ujfalusi is out until the new year with a knee problem while Spanish winger Albert Riera is also set to sit out the clash with the Portuguese.