Marcos returned to the site of his first ATP World Tour final, at the Swiss Indoors in Basel, but was unable to fight past fifth seed David Goffin.
Goffin prevailed 6-4, 7-6(4), earning the first round victory with an immediate break to open the match and an early mini-break in the second set tie-break. Marcos held a pair of set points at 5-4 in the second set.
The victory was just Goffin’s second win over Marcos in six head-to-head clashes.
Marcos will conclude his 2016 ATP World Tour campaign at the final Masters 1000 event of the year – the BNP Paribas Masters in Paris. Currently at No. 36 in the Emirates ATP Rankings, Marcos will look to finish a season in the Top 40 for the first time since 2012.