Nieminen handled Lukas Lacko 6-3, 6-1 while winning 61 percent of the points on serve and finishing off five of his nine break opportunities.
He took more than 60 percent of the points, including losing six points in three service games, in putting the match away in the second set.
Andre Ghem, No. 260 in the rankings and a qualifier in Dusseldorf, picked up his first ATP World Tour match win of the year with a 6-4, 6-0 win over Go Soeda. Ghem claimed 80 percent -- all but six -- of the points in the second set.
Also Monday, Guido Pella topped Lukasz Kubot 6-4, 4-6, 6-4; Tobias Kamke beat Benjamin Becker 6-3, 6-2; and Roberto Bautista Agut got past 2-6, 6-4, 6-2.