Bank and resource stocks also succumbed to that pressure.
By 1500 GMT the rand was down 0.3 percent at 13.7975 per dollar, less of a fall than expected as the greenback wavered following weak jobs data.
The rand has fallen more than 11 percent since March 27, when President Jacob Zuma recalled Gordhan from an investor roadshow to Britain and the United States.
"Either the market has fully priced-in the downgrades or it believes that this is good for the country and that it might eventually see President Zuma forced out of office," Nedbank senior economist Isaac Mashego said.
Fitch on Friday followed S&P Global Ratings and downgraded South Africa to "junk", citing Gordhan's dismissal as one reason. S&P had issued its downgrade on South Africa in an unscheduled review on Monday.
Following the downgrades, J.P. Morgan said it would drop South Africa from its investment-grade emerging market bond indexes by late April.
The ratings agency moves are likely to force international tracker funds, or funds prohibited from holding sub-investment grade securities, to sell South African assets.
On the bourse, the benchmark Top-40 index fell 0.18 percent to 46,085 points while the All-Share index dipped 0.12 percent to 52,853 points.
The mining index fell 0.58 percent on the back of weaker iron ore prices, while the banking index fell 0.39 percent after the Fitch downgrade. [nL3N1HF2V7}
"The iron ore price is down quite a bit, so sentiment towards these resource shares is a little weaker," Cratos Capital equities trader Greg Davies said.
Among the biggest fallers, ArcelorMittal fell 7.30 percent to 9.65 rand, Kumba Iron Ore dropped 4.19 percent to 214.65 and African Rainbow Minerals lowered 2.79 percent to 100.61.
Losses were curbed by gains in gold miners' shares, which benefited from bullion prices climbing to five-month highs.
Goldfields rose 6.30 percent to 53.00 rand and AngloGold Ashanti climbed 3.84 percent to 170.81.
In the fixed income market, bond prices were firmer on the day as high yields attracted some buying. Benchmark yields on bonds due in 2026 dropped 9 basis points to 8.93 percent.