De Haas, 26, joins from Famalicão, and Dieng, 28, arrives from Egyptian giants Al-Ahly after six years in Cairo, where he won the CAF Champions League four times. Both deals are free transfers, fitting Valencia's austere transfer policy as the club nears a second consecutive season of survival after years of financial turmoil.
Corberán was asked at his pre-match press conference about his role in convincing the new arrivals to choose Valencia.
"Nobody comes to Valencia because of Carlos Corberán. It's impossible. People come for the same reason I came — the greatness of the badge. The confidence that (Arnaut) Danjuma had in me was not the reason he came. Sometimes it can help to frame a situation, but I like to talk to footballers about football. Investing time with them is very productive."
He was unambiguous about where the club's appeal truly lies.
"The Valencia badge and history convinces. Not me. It's the club, the crest, the greatness of the club."
Dieng joins as a holding midfielder, addressing a gap in Corberán's squad that became clear over the course of the season. His arrival is particularly significant given the uncertainty surrounding Argentine midfielder Guido Rodríguez, who signed only until the end of the current campaign and whose future at the club has yet to be resolved.
De Haas was confirmed first, with chief executive Ron Gourlay having publicly signalled a second signing was imminent before Dieng's name emerged. Both players will arrive in July ahead of pre-season.
Valencia sit five points above the relegation zone with five games remaining, on the verge of confirming their top-flight status for another year. The early recruitment suggests the club is building with more stability in mind than in recent windows.