Marcos is back in Germany for a two-week grass-court stretch, beginning on Monday with the MercedesCup in Stuttgart. He opens against last year's finalist Philipp Kohlschreiber.
Marcos continues his quest for his first victory on grass this year, facing the German for the eighth time. Marcos, who leads their head-to-head 5-2, won their most recent meeting at the Masters 1000 event in Miami in 2014. He has also taken both their encounters on grass, in the 2006 's-Hertogenbosch quarter-finals and 2007 Halle semi-finals.
A first-round victory would see Marcos face either fifth seed Steve Johnson or German wild card Maximilian Marterer. Second seed Grigor Dimitrov and fourth seed Lucas Pouille are also in his half of the draw, with top seed Roger Federer leading the charge in the other half.