At the beginning of the Ryonan-Shohoku game, Sakuragi does a basket interfere as he doesn't know it's against the rules. He starts protesting loudly etc, and who comes along to stop him from getting a technical foul? Why, it's Rukawa!

Sakuragi falls after a confrontation with Uozomi mid-dunk. Might I ask what the hell is Rukawa doing there? (Note: Sendoh's there, too. My warped imagination supplies --> Rukawa: "Stay away, Sendoh, if anyone's comforting my do'aho, it'll be ME.")
 

My, my, my, Rukawa's turning into a chatterbox, ain't he? Sakuragi's having some trouble with the super-scorer Fukuda, and so Rukawa happily jumps in to give him a gentle push in the right direction with a few words.

Just after Ayako breaks up another Rukawa-Sakuragi fight, she tells the red-head that Haruko was so concerned when he was injured during the game. Just then Akagi's eyes move from (a fawning-over-Haruko) Sakuragi to (a nonchalant-looking) Rukawa, as though the captain is wondering what Rukawa's thinking of Sakuragi's attentions toward Haruko. 
 
 

Sakuragi lets Ikegami pass him rather easily, and as Sakuragi's berating himself, he turns to see Rukawa staring at him. *cough cough cough* (Note: Rukawa doesn't insult him this time, either.)
 

Rukawa gets a free-throw thanks to Sendoh's foul. As he's about to take it, he looks at Sakuragi and says, "I will beat Sendoh." This is strange, considering that Rukawa could have passed the statement to Sendoh directly (who was standing next to Sakuragi) and it can't be a warning either as Sakuragi hasn't gotten in Rukawa's way at all. So what's up with the proclamation?

Me being me, I go with my opinion that Rukawa wants to beat Sendoh because of Sakuragi. (So my brain adjusts Rukawa's line to be: "I will beat Sendoh for you.")