Punjab Kings shelled out $2.23million on the all-rounder but they are eighth in the 10-team table and barring a miracle will not qualify for the knock-out phase.
With a week of the group phase left, Curran was languishing at 39th on the runs table as of early Monday, with 216 from 11 innings and only one half-century.
South African six-machine Faf du Plessis (38) at Bangalore has almost three times as many runs and seven 50s to top the batting stats.
Left-arm quick Curran, who with his run-choking bowling at the death was player of the tournament at the T20 World Cup last winter, has been even less effective with the ball.
He has seven wickets (51st position) at an economy of more than 10.
Former India opener Virender Sehwag (44) was the latest commentator to lay into his sub-par performance, comparing him unfavourably with bargain-buy teammate Prabhsimran Singh (22) after the Indian player's century on Saturday.
"You bought Sam Curran for $2.23million, what has he done?" Sehwag told the website Cricbuzz.
Sehwag, known for his straight talk, also criticised Curran last month, saying "he doesn't have that experience yet" despite the record-setting price tag.
Curran, who had a previous stint in the IPL with Chennai Super Kings, started this edition of the competition well.
He captained Punjab in three matches in the absence of the injured Shikhar Dhawan (37) and played match-winning roles in two of them.
Bowling figures of 3-31 - his best this season - helped Punjab down Lucknow Super Giants and then his 29-ball 55 won him the player of the match award against the Mumbai Indians.
Curran tried to make light of the fee Punjab paid, telling Sky Sports last month: "They've put a lot of faith in me and I guess I'm the type of person try not to put too much pressure on myself.
"Hopefully I can show some good performances for the team. The price tag is what it is."
But Curran has since struggled with the pitches and conditions, and on Saturday pundit Simon Doull picked him as his biggest disappointment of the current IPL season.
"Sorry Sam Curran. It's you this season so far," the former New Zealand paceman said.
"Hasn't bowled well enough at the death, going at over 10 an over. You buy a big-priced all-rounder, you have to deliver."
'A little disappointed'
Curran is not the only big buy to disappoint.
Australian all-rounder Cameron Green (23) has been decent if not spectacular, hitting 274 runs to help Mumbai to third in the table, but taking only six wickets.
Green was the second most expensive buy in the December auction after Mumbai Indians paid out 175 million rupees ($2.11 million) on him.
Several Englishmen have failed to live up to the hype - a worry for the country ahead of the Ashes and one-day World Cup.
England Test skipper Ben Stokes (31) was bought by Chennai Super Kings for 162 million rupees but managed only two underwhelming performances before being benched with injury.
Harry Brook (24) is another Englishman who has not been at his destructive best, despite hitting the first century of this edition last month.
Brook, who was snapped up by Sunrisers Hyderabad, has scored just 63 runs in eight matches.
The right-handed batsman is 51st in the runs table.
"I was very, very excited to see Harry Brook," Indian commentator Harsha Bhogle said.
"I thought Brook and SKY (Suryakumar Yadav), these were the two players I thought, 'Wow! Let's see them go head to head.
"I saw (Brook's) hundred in Kolkata but I am a little disappointed by what followed."
