Right Concentration

In the suttas, whenever the Noble Eightfold Path is analyzed, right concentration is usually defined as the four jhānas. For example in Vibhaṅga Sutta in Magga Saṃyutta (Saṃyutta-Nikāya, Maggasaṃyutta, Sutta 8):

“And what, bhikkhus, is right concentration? Here, bhikkhus, (1) completely secluded from sense pleasures, secluded from unwholesome states, a bhikkhu enters and dwells in the first jhāna, which has initial-application, and sustained-application, with joy and bliss that are born of seclusion; (2) With the subsiding of initial-application and sustained-application, he enters and dwells in the second jhāna which has inner clarity and unification of mind, which is without initial-application and sustained-application, which has joy and bliss born of concentration; (3) With the fading away as well of joy he dwells equanimous, mindful and clearly comprehending, and he experiences bliss with the body; he enters and dwells in the third jhāna of which the Noble Ones declare ‘He is equanimous, mindful, one who dwells in bliss;’ (4) With the abandoning of pleasure and pain, and with the previous disappearance of happiness and unhappiness, he enters and dwells in the fourth jhāna which is without pain and pleasure, a [state of] purity of mindfulness due to equanimity. This, bhikkhus, is called right concentration.”

From this and similar passages (e.g. Dīgha-Nikāya Sutta 22, Majjhima-Nikāya Sutta 141, Vibhaṅga Saccavibhaṅga) it seems that right concentration of the Noble Eightfold Path must necessarily consists of the four jhānas. But is this always the case? Can right concentration be some concentration other than these samatha jhānas?