The Italian champions were imperious in eliminating Chelsea in the last 16 with a 1-0 win in London but their recent Serie A form has been poor by comparison.
Their lead at the top has been cut from nine points in mid-February to just a point following Saturday's 2-1 defeat at title rivals AS Roma, where Inter hit the woodwork three times but looked much more nervous than usual.
"Playing every three days isn't easy but our desire to win is stronger than the tiredness," Inter's leading scorer Diego Milito said ahead of the San Siro clash.
"Every match is hard and we mustn't underestimate anyone. We just have to think about ourselves."
They should be at full strength with Chile winger Mark Gonzalez looking to shake off the muscle spasms which forced him to miss Friday's league win at Anzhi Makhachkala.
Full back Vasily Berezutsky was hoping the Italians would underestimate his side, who shocked many pundits by eliminating Spain's Sevilla in the previous round.
"Inter were probably very happy after being drawn to face us," the Russian international told Moscow media.
"I think they were already dreaming of a place in the semi-finals. That should suit us just fine. Sevilla also looked very confident prior to our matches but where are they now?"
"We were told that Mourinho was in the stands so we tried to conceal our strengths on purpose," he said, referring to a drab 0-0 draw.
Inter Milan: 12-Julio Cesar; 13-Maicon, 2-Ivan Cordoba, 25-Walter Samuel, 26-Cristian Chivu; 4-Javier Zanetti, 19-Esteban Cambiasso, 5-Dejan Stankovic; 10-Wesley Sneijder; 9-Samuel Eto'o, 22-Diego Milito
