Sheyi Ojo bundled home a 70th-minute leveller with Boro convinced that referee Jon Brooks had missed George Saville, their first-half scorer, being blocked off at a corner.
“I’m disappointed with the goal as it’s an obvious foul,” said Warnock, who left Cardiff last November after three years in charge.
“They’ve blocked Saville to give Kieffer Moore a free header. Referees at this level should be able to see things like that.
“It’s a disgrace really after last Saturday’s offside that wasn’t offside. That’s four points we’ve thrown away this week with decisions. I’m disappointed because I thought we did enough to win it.”
Veteran boss Warnock won a record eighth promotion during his time at Cardiff. “I was told they’d changed style since I’d left,” Warnock said. “I’m not sure the style of football has changed if I’m honest.
“They’re the best physical side and the towel’s round the side with every throw-in.
“It was weird getting off the bus and seeing one or two staff when I was there. I’ll come back even when I retire to watch a game. I’ll have a walk round and thank them, they were amazing to me.
“But life goes on, it was the right time for me to leave. I’d done everything I could.”
Boro have gone six Championship games unbeaten since an opening-day defeat at Watford and Warnock has certainly made them harder to beat.
Cardiff: Smithies, Osei-Tutu (Bacuna 67), Morrison, Nelson, Bagan, Ralls, Vaulks, Ojo (Hoilett 86), Wilson, Murphy (Glatzel 63), Moore. Unused substitutes: Phillips, Whyte, Pack, Bamba.
Middlesbrough: Bettinelli, Dijksteel, Fry, McNair, Howson, Tavernier, Morsy, Saville, Bola, Akpom (Assombalonga 66), Johnson (Spence 77). Unused substitutes: Wing, Browne, Roberts, Stojanovic, Coulson.
Referee: J Brooks (Leicestershire).
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