Smeltz was shown a straight red card late in the Sky Blues' 3-0 victory over his former club Wellington Phoenix at Westpac Stadium on Sunday after lashing out with his foot at Ben Sigmund.
Football Federation Australia's match review panel on Monday determined Smeltz had committed the offence of 'assault on a player' and proposed the minimum sanction for the offence of two matches, 'being the Mandatory Match Suspension plus one (1) additional match'.
Sydney can ill afford any setbacks with the race to the top - the tightest it has ever been - with only two points separating the top five sides.
Sydney sits just one point behind ladder leader Phoenix and is level on points with both Melbourne Victory and Perth Glory with four rounds remaining.
Smeltz will miss Sydney's clashes with Adelaide United and Perth Glory but will be back for its matches against Newcastle Jets and Wellington.
Smeltz has mainly been used as an impact player off the bench this campaign and was making just his eighth start on Sunday in place of marquee striker Marc Janko who was away on international duty.
His 28th-minute strike on Sunday was his seventh for the season.
