Takashi Shimura did not receive an Oscar nomination for portraying Doctor Sanada in Drunken Angel.
Now Shimura does play the part as the more morally righteous figure against Mifune, which was typically their dynamic pre-1960's. The role of Doctor Sanada though is not played by Shimura as a quietly earnest stoic sort. He is, after all the titular character, the "Drunken Angel", obviously a good man but also...a drunk. Shimura doesn't at all conduct himself as the "hero" even in the opening scene where we see him treating Mifune's gangster's bullet wound. Sanada purposefully makes it a painful operation while openly boasting about planning on overcharging. Shimura delivers this in turn portrays a complete lack of empathy in this initial moment, as he wraps every glance and delivers with a clear disgust. Shimura reacts not so much in a personal way, rather his demeanor illustrates a man viewing this gangster as he views any other lowlife. Shimura portrays this as a man having no waste of sympathy even creating a very real intensity in his eyes as he looks as his patient writhing in pain that he is inflicting. This isn't even lost by Shimura as Sanada pesters the man over a cough that may be tuberculosis. Shimura delivers this with mocking, though not overly so, tone again reinforcing the man irritability towards such wasteful men.
The opening scene reveals a darker side in Shimura's performance, however he does reveal the titular angel while Sanada gives Matsunaga a TB exam. Once Sanada discovers that the man may have the deadly disease, Shimura subtly pulls back on the disgust to develop the right hint of sympathy given the severity of the situation. Although Shimura does not wholly open up, he is particularly effective in his approach by so quietly assuming just the right hints of concern in his eyes, and even in his softer delivery while still speaking words mostly dismissive of the gangster. Shimura naturally reveals the good heart that defines Sanada, however this first scene is not an outlier in terms of portraying this rougher side of the character. Shimura, even as Sanada is on a theoretically positive duty to inform the gangster of his condition, portrays essentially this struggle between the man's virtues and his vices. Shimura is fascinating to watch here as his performance is so physically expressive, arguably more so than Mifune in this film which is saying something, and he thrives in this approach.
Now to be fair Shimura is always an expressive actor however this is usually honed within his face, although there's that of course which I'll get to, he is remarkable in his depiction of Sanada as this sous. Shimura doesn't hold back in this regard showing an absolute lust in his moments of drink as a man who is wholly desperate in this act as a severe addiction. Shimura even develops the man's physical stature as this weakly in how he shows that Sanada is indeed menaced by Matsunaga's violent outbursts. Although he doesn't show a man who truly cowers as he brings still such a palatable resilience in his delivery in these moments, however he doesn't hide the physical weakness of the man that reveals a genuine fear, if even mostly from instinct. The weaknesses of the man do not come from interaction with the troublesome individuals that live in his slum. Shimura delivers the difficulty of the man's experience at every point as this contradiction. There's wonderful slight moment early on as he looks for Matsunaga explaining he is the type of guy women go for. Shimura's whole manner is that of a defeated man, and even in his sardonic line of how women should prefer him, there is real pathos in Shimura's eyes that allude to perhaps more honestly within that sentiment than he would care to admit.
Sanada as a character, in turn is the noble sort in nearly all of his actions but no in attitude. Again Shimura is excellent in the way he brings to life this angle defined by his demons. His interactions rather with Mifune are great throughout the film, and very different from their typical dynamic. In this one when Mifune barks, Shimura barks right back at him which is rather remarkable. Shimura expresses so well Sanada not as a man who calmly informs people to do the right thing, rather demands it. Shimura again delivers this intensity of a man nearly broken by his circumstances whose outrage goes beyond a single case such as Matsunaga, but rather is screaming towards everyone who has failed to make use of his good will. This is in stark contrast to the few, yet important, moments where we see Sanada with another one of his TB patients who is actually listening to his orders for recovery. In these moments Shimura reveals such a quiet and quiet powerful realization of the sheer warmth within the man when it isn't hidden by his anger. An anger that Shimura reveals perhaps even deeper than at society but also perhaps against his own problems. Shimura never hides the pathetic nature of his character, even as he does unquestionable good.
The crux of the film comes as Matsunaga attempts reformation by trying to take on a former gang boss of the neighborhood, while also dying from his TB. Meanwhile Sanada only keeps his attempt to save the man essentially by yelling him into submission, while also dealing with the gang boss who is looking for his old girlfriend who happens to be the doctors assistant. Shimura effectively presents Sanada as a constant in these scenes showing that the man doesn't change his approach even when threatened with death. Matsunaga is instead the one to take action that leads to his death, though also does lead to the imprisonment of the gang boss once again. This leaves a final scene for Shimura which is one of the best of his career. It is an amazing scene as he keeps on bringing Sanada's temper into the moment, though calmed a bit, as he espouses his hatred of the way and waste of the Yakuza gangsters. His voice is disparaging, yet Shimura in that expressive face of his reveals the very real heartbreak in Sanada over the loss of his patient that delivers this final poignancy on his relationship with the gangster. Shimura delivers a great performance here as he finds essentially the diamond in the rough, not as a hero in a slum, but rather the kindness within a wretched man.