User blog comment:B214/Volume 23 discussion blog/@comment-31137559-20170410043119/@comment-10330822-20170411044524

Tien goes from a very serious threat and rival to a close friend of Goku's, so honestly, Sairaorg is more like Tien than anyone. Saji, like Yamcha, was never really a threat to Issei, while Sairaorg was a very serious threat in his part of the story.

If we are putting characters to characters. Saji is like Yamcha, Kiba is like Krillin, Sairaorg is like Tien, and Vali is like Piccolo. Cao Cao is more like the Vegeta of this series, where he's a villain by not really befriended by the MC. Then again, you could interchange Vali with Vegeta, and Cao Cao with Piccolo, and get pretty much the same result.

Note, these comparisons aren't to deminish what the DxD characters are contributing to the series, nor is it a perfect reflection. But, you have to admit Krillin was always an ally of Goku's, and probably a much better rival than Yamcha, just like Kiba is a much better rival than Saji is. Sairoarg as Tien is pretty much nail on the head, where he is a seasoned warrior while Goku/Issei is a newbie in the martial arts world.

Granted, as Pawn was mentioning, the DxD characters are doing more regularly than the DBZ characters did. So, even though Tien was pretty important in the Piccolo Saga and in a lesser extent Saiyan Saga, he still falls into the same support role as Yamcha. The only difference is Tien really shinned as a character and true rival for a bit, while Yamcha could barely ever be called a true rival.