| League: | MPBL / PSL |
| Height Ft: | 5 |
| Height In: | 8 |
| Weight Lb: | 150 |
| Team: | Nueva Ecija Rice Vanguards |
| Position: | Head coach |
| Nationality: | Filipino / American |
| Birth Date: | 17 October 1980 |
| Birth Place: | Los Angeles, California, U.S. |
| Draft Year Pba: | 2006 |
| Draft Pba: | Undrafted |
| College: | El Camino College |
| Career Start: | 2007 |
| Career End: | 2013 |
| Career Position: | Point guard |
| Coach Start: | 2017 |
| Years1: | 2007–2010 |
| Years2: | 2011 |
| Years3: | 2012–2013 |
| Cteam1: | Rain or Shine Elasto Painters (assistant) |
| Cyears1: | 2017–2018 |
| Cteam2: | Davao Occidental Tigers |
| Cyears2: | 2018–2021 |
| Cteam3: | Makati OKBet Kings |
| Cyears3: | 2023 |
| Cteam4: | Nueva Ecija Rice Vanguards / Capitals |
| Cyears4: | 2024–present |
| Highlights: |
Donald Isidro Merza Dulay[1] (born October 17, 1980, in Los Angeles, California) is a Filipino-American former professional basketball player. He is the current coach of the Nueva Ecija Rice Vanguards franchise of the Maharlika Pilipinas Basketball League (MPBL) and the Pilipinas Super League (PSL). He was an undrafted player but was later signed by Rain or Shine in 2007. He is also given the moniker "Double D" because of the D's in his first name and surname.
Dulay applied for the 2006 PBA draft but no team drafted him.[2] He was signed by the Welcoat Dragons as a free agent in the 2007–08 PBA season. Dulay, known in local Philippine basketball as ‘Double D’, plays Guard and stands 5’8″. Born and raised in Los Angeles, California, he moved to the Philippines to pursue his basketball career. Dulay starred for Cebuana Lhuillier and Welcoat Dragons in the Philippine Basketball League (PBL) before bringing his struts to the Philippine Basketball Association (PBA), where he played for the Rain or Shine Elasto Painters and the Alaska Aces.
|-| align=left| | align=left| Welcoat| 33 || 13.9 || .321 || .256 || .583 || 1.2 || 2.0 || .3 || .0 || 3.8|-| align=left| | align=left| Rain or Shine| 40 || 14.7 || .333 || .328 || .656 || 1.4 || 1.6 || .2 || .0 || 4.4|-| align=left| | align=left| Rain or Shine| 16 || 10.1 || .403 || .350 || .733 || 1.4 || 1.3 || .2 || .0 || 4.7|-| align=left| | align=left| Alaska| 3 || 5.7 || .000 || .000 || — || .0 || .0 || .0 || .0 || .0|-class=sortbottom| align=center colspan=2 | Career| 92 || 13.3 || .335 || .305 || .639 || 1.3 || 1.6 || .2 || .0 || 4.1