Jose Mourinho said neither Lucas Moura nor Son Heung-Min are adequate replacements for injured striker Harry Kane after watching his Tottenham side draw 1-1 at Middlesbrough in the FA Cup.
Lucas scored a second-half header to level the match at the Riverside Stadium, where an Ashley Fletcher strike had put Middlesbrough ahead in a game that left Mourinho "frustrated".
Tottenham are without a win in their last three games in all competitions and Mourinho said injuries to Kane, Tanguy NDombele, Hugo Lloris and Danny Rose were hampering his side's progress.
After starting the game with Son as a lone striker and later moving Lucas up alongside him in a front two, Mourinho told reporters: "We have what we have and we stick with them. The boys did what they can.
"You cannot transform Lucas or Son in a number nine like Harry Kane."
"We changed things and took our risks. Our team in the last 30 minutes we didn't even have a midfield player," added Mourinho, referring to his decision to replace Harry Winks and Ryan Sessegnon with Giovani Lo Celso and Erik Lamela.
"We played with six attacking players without a striker. We took our risks."
Tottenham are sixth in the Premier League despite having lost three and drawn one of their last seven games in the competition, and Mourinho admitted the cup brought little respite on a frustrating afternoon.
Away form is a particular problem for the Portuguese coach, whose side have won two of their seven games on the road since he took charge on November 20, and he said earning a replay on home turf against Middlesbrough was no disaster.
"Sometimes the same way players are frustrated on the pitch, I was frustrated on the touchline," said Mourinho. "Everyone in the stadium had a real cup match.
"It was a difficult match. If football was about how many times you arrive in scoring positions, we would win by a huge score.
"1-1 is not a disaster. We take the game home. We are in trouble with so many injuries. I took the players today that are available."