Soderling, the only seed to reach the last eight, again played before a boisterous sellout center court crowd at Royal Tennis Hall. The 10th-ranked Swede, a surprise French Open finalist, will play Marcos Baghdatis of Cyprus in one semifinal on Saturday.
Baghdatis ousted French qualifier Arnaud Clement 6-4, 6-4.
After Soderling and Garcia-Lopez traded service breaks, Soderling took a 3-0 lead in the tiebreaker and eventually won it 7-4 when the Spaniard hit a backhand slice wide.
Soderling broke for 1-0 in the second set and held his serve the rest of the way.
"He played really well, he's a lot better than his ranking shows," Soderling said of the 49th-ranked Garcia-Lopez.
Rochus broke Nieminen's serve to open their third set. He broke again to lead 3-0 after a couple of unforced errors by the Finnish left-hander, and won the match when Nieminen double-faulted on match point.
Johansson was playing in only his second tournament this year in a bid to comeback from shoulder injuries. The former top-10 player was ranked 511th coming into the event.
He fell behind 1-0 at the start of the tiebreaker against Bellucci after neither player managed to break serve in the opening set. That was all Bellucci needed, racing 3-0 ahead and eventually clinching the set when the Swede netted a volley.
Bellucci broke for a 3-1 lead in the second, and Johansson blew a chance to break back in the seventh game, netting a backhand return at break point. The Brazilian held serve to close out the match.