What if Nobunaga was defeated heavily at Akatsuka and Kayatsu in 1552? The chances of Nobunaga unifying the Oda house would have been slim. Owari would have been different. I do agree with Cody with the Imagawa factor. The Oda house would have been so weak that the Imagawa would have played a major role in Owari. I think the Oda house would do anything to save their own rear ends. Just as the Imagawa made the Matsudaira bend, the Oda would have to the same.
Three golden rules in Sengoku Japan.
1) Fight your way to the top
2) Have an alliance with an equal partner
3) Submit to a higher authority
I think the Oda would have to submit to the Imagawa. Yoshimoto had Mikawa and Owari would have been a key province for many reasons. Could Nobunaga have any support from his father-in-law, the Viper of Mino Saito Dosan? Who knows. Maybe. Up in the air. It would only be year later where the two would finally meet at Shoutokuji in Tonda (1553).
Instead Nobunaga triumphed at the Battle of Akatsuka and Kayatsu. The two battles would be key to unifying Owari and the Oda clan. With the murder of Shiba Yoshimune the Owari shugo in 1554 by Oda Nobutomo and Sakai Daizen paved the way for Nobunaga taking Kiyosu Castle in 1555. It did several things. Oda Nobutomo was killed and the Nobunaga was the sole commander of the Kiyosu Castle which was the home base of the Oda Kiyosu branch. Also Kiyosu Castle would be the area where Nobunaga could attack the Oda Iwakura branch. Four years later 1559, Nobunaga finally was the sole ruler of Owari when he attack and destroyed Iwakura Castle. The Oda Iwakura branch was gone and Nobunaga finally united the Oda family and Owari.
It would not have been possible without the victories of Akatsuka and Kayastu in 1552.
Tenka no Tame!