“Shams al-Din al-Dhahabi”, one of Sunni scholars says about Imam “Baqir” [AS]:

ابوجعفر الباقر ،سیّد امام فقیه،یصلح للخلافة؛

“Abu Ja’far al-Baqir”, lord, imam, faqih, and He’s the one who was competent for caliphate.

Syar al-A’lam al-Nubala’- vol. 13, p 120