Lifespan: Unknown to 11/27 of Tenbun 7 (1538)
Other Names: Yoichi, Naizen-no-kami (common)
Lord: Matsudaira Nobutada → Matsudaira Kiyoyasu → Oda Nobuhide (according to one theory) → Matsudaira Hirotada
Father: Matsudaira Nagachika
Siblings: Nobutada, Chikamori, Nobusada, Yoshiharu, Toshinaga
Wife: Daughter of Matsudaira Chikafusa
Children: Kiyosada, daughter (wife of Matsudaira Chikanori), daughter (wife of Mizuno Nobumoto), daughter (second wife of Matsudaira Yasutada), daughter (wife of Oda Nobumitsu)
Matsudaira Nobusada served as a bushō during the Sengoku period. Nobusada was the first head of the Sakurai-Matsudaira family based in the village of Sakurai in the Hekikai District of Mikawa Province. The Sakurai-Matsudaira were an illegitimate branch of the Matsudaira clan founded by Matsudaira Nobusada, the second son of Matsudaira Nagachika, the fifth head of the main branch of the Matsudaira clan. Regarding the headship of the main branch of the Matsudaira clan, Nobusada first came into conflict with his eldest brother, Matsudaira Nobutada, and his opposition extended over three generations to include Matsudaira Kiyoyasu and Matsudaira Hirotada, but Nobusada lost.
At the end of the fifteenth century, Nobusada was born as the third son of Matsudaira Nagachika of the main branch of the Matsudaira. Under another theory, he was the second son. Although Nobutada inherited the headship of the clan, he was not a popular figure among the family members or retainers, and, further, lacked the skills to serve as the commander-in-chief. As a result, there was a leadership deficit in the Matsudaira clan. Voices were then raised in support of Nobusada, as the third son of Nagachika, to become the designated successor of Nagachika who also viewed Nobusada as a potential successor. Nobusada, however, was sent to become an adopted son-in-law of his uncle, Matsudaira Chikafusa (the fourth son of Matsudaira Chikatada), so he was dropped as a nominee to inherit the headship of the main branch of the Matsudaira and, instead, built his base at Sakurai Castle on the territory of his uncle in Sakurai in the Hekikai District of Mikawa. Later, Nobutada inherited the headship of the clan, but following criticism from family members and retainers for being an imbecile, was soon be forced into retirement. Nobutada was then succeeded by his son, Matsudaira Kiyoyasu.
In 1523, following Kiyoyasu’s succession, Nobusada entered into his service. Nobusada did not, however, did not adopt a subservient posture toward the clan. In 1526, he established relations with the Oda clan who served as the lords of Moriyama Castle in Owari Province and were antagonists of the Matsudaira. To do so, Nobusada arranged for his lineal heir, Matsudaira Kiyosada, to wed the younger sister of Oda Nobuhide and, later, sent his daughter to wed Oda Nobumitsu.
Under the command of Kiyoyasu, in 1529, Nobusada toppled Shinano Castle (the base of Sakurai Hidetada, a retainer of Nobuhide) and made it his base, but, from around this time, Nobusada began to display disquieting actions toward Kiyoyasu. Kiyoyasu turned the direction of his external campaigns toward eastern Mikawa which was under the control of Imagawa Ujiteru and, in 1530, joined in an assault against the base of Kumagai Sanenaga at Uri Castle in the Yana District. According to accounts of Mikawa written in the early Edo period, Nobusada fought with his second oldest brother, Matsudaira Chikamori, as members of the units attacking the main gate of Uri Castle, but, as the tide turned against Chikamori, did not, under the pretext of illness, send forces to his aid, so Chikamori and his son were killed. Having witnessed these developments from the main base, Kiyoyasu became upset and, after the battle, reproached Nobusada in front of many others. According to one theory, Nobusada deeply regretted the action. Further, that same year, during an assault against the base of Makino Nobushige at Yoshida Castle, while clashing against defenders on the west bank of the castle in Shimoji in the Hoi District, Kiyoyasu sought to charge the enemy to overcome a disadvantage at the outset of hostilities, whereupon Nobusada said “Let’s have the general die in battle” and purposefully did not restrain him.
In 1535, Kiyoyasu was unexpectedly slayed by a retainer while on an expedition in Moriyama in Owari Province. This event is known as the Collapse at Moriyama. In the wake of the killing, Nobusada, who did not join this expedition (according to one theory, he was colluding with the Oda), took advantage of the resulting chaos in the Matsudaira clan and came into conflict with Takechiyo (Kiyoyasu’s orphan later known as Matsudaira Hirotada) to become the successor of Kiyoyasu as the head of the clan. Nobusada then occupied Okazaki Castle which had served as the base for Kiyoyasu as well as Takechiyo. Under the protection of his retainers, Takechiyo fled for safety to Ise Province.
Through the efforts of an attendant of Hirotada named Abe Sadayoshi, Imagawa Yoshimoto, the sengoku daimyō of Suruga Province among others, offered support in response to a proposal from Kira Mochihiro of the Tōjō-Kira clan. Hirotada and his retainers met with Yoshimoto in Suruga and, the following year, with the help of reinforcements from the Imagawa army, entered Muro Castle in the Hazu District. Fearing the recapture of Okazaki, Nobusada attacked but failed. Hereditary retainers including Ōkubo Tadatoshi remaining in Mikawa who were members of Hirotada’s faction supported the return of Hirotada to Okazaki. In the sixth month of 1537, Matsudaira Nobutaka (Nobusada’s nephew and a member of the Mitsugi-Matsudaira family), who remained to guard Okazaki Castle, switched his allegiance to Hirotada and welcomed Hirotada to Okazaki Castle. Aware that the circumstances had turned against him, Nobusada then submitted to Hirotada.
Despite a simmering down of the internal struggle over leadership of the Matsudaira family, Nobusada maintained an attitude toward Hirotada that was far from subservient. This led to conflict with his younger brother, Matsudaira Yoshiharu, who was in the faction backing Hirotada. Nobusada died on 11/27 of Tenbun 7 (1538).
His eldest son, Matsudaira Kiyosada, and grandson, Matsudaira Ietsugu, expressed opposition toward the main branch of the clan, but, in the spring of 1564, accompanying the end of the Mikawa Ikkō-ikki, fully reverted to the main branch.