Have a look at this scorecard- the 18 year old Richardson did show signs of ability with some useful runs batting at no.10, and he also bowled none other than Kapil Dev, and the 16 year old SR Tendulkar! I think this underlines that he wasn't just any left arm-spinner, but probably the best in the country for his age by some margin.
India in New Zealand 1989-90
New Zealand Presidents XI v Indians
Pukekura Park, New Plymouth
22,23,24,25 January 1990 (4-day match)
Result: Indians won by 159 runs
Toss: Indians
Umpires: RS Dunne and SJ Woodward
Indians 1st innings
VB Chandrasekhar c Thomson b Larsen 92
NS Sidhu c White b Thomson 23
SV Manjrekar c Parore b Thomson 80
*M Azharuddin c Bradburn b Thomson 159
SR Tendulkar c Richardson b Millmow 13
M Prabhakar c Douglas b Millmow 24
N Kapil Dev c Rutherford b Millmow 25
+KS More not out 45
SLV Raju c Parore b Millmow 3
V Razdan c Snedden b Millmow 18
ND Hirwani c Rutherford b Thomson 11
Extras (b 4, lb 11, nb 4) 19
Total (all out, 119 overs) 512
FoW: 1-77, 2-150, 3-268, 4-298, 5-394,
6-430, 7-432, 8-436, 9-475, 10-512.
Bowling O M R W
Millmow 27 3 127 5
Thomson 29 6 108 4
Rutherford 3 0 29 0
Snedden 12 2 46 0
Larsen 19 6 53 1
Richardson 16 0 61 0
Bradburn 13 1 73 0
New Zealand Presidents XI 1st innings
KA Wealleans lbw b Prabhakar 0
DJ White run out 20
KR Rutherford c Manjrekar b Kapil Dev 54
M Douglas c More b Raju 30
GE Bradburn c More b Prabhakar 74
GR Larsen lbw b Prabhakar 43
SA Thomson c Azharuddin b Kapil Dev 24
+A Parore c Prabhakar b Hirwani 22
*MC Snedden c More b Prabhakar 16
M Richardson not out 29
J Millmow not out 4
Extras (lb 7, nb 6) 13
Total (9 declared, 111 overs) 329
FoW: 1-2, 2-59, 3-93, 4-150, 5-225,
6-234, 7-280, 8-280, 9-319.
Bowling O M R W
Kapil Dev 20 6 48 2
Prabhakar 23 4 87 4
Razdan 13 2 76 0
Raju 27 11 68 1
Hirwani 28 12 43 1
Indians 2nd innings
VB Chandrasekhar b Thomson 3
NS Sidhu c Parore b Snedden 30
SR Tendulkar b Richardson 47
SV Manjrekar c Rutherford b Larsen 11
M Prabhakar c Snedden b Richardson 1
N Kapil Dev b Richardson 0
*M Azharuddin run out 24
+KS More not out 59
SLV Raju c Parore b Thomson 9
V Razdan c Bradburn b Thomson 0
ND Hirwani c & b Bradburn 0
Extras (lb 1) 1
Total (all out, 57.5 overs) 185
FoW: 1-23, 2-59, 3-87, 4-88, 5-92,
6-93, 7-143, 8-172, 9-172, 10-185.
Bowling O M R W
Millmow 5 0 15 0
Thomson 13 0 56 3
Snedden 8 3 12 1
Larsen 15 3 45 1
Richardson 11 2 47 3
Bradburn 5.5 1 9 1
New Zealand Presidents XI 2nd innings
DJ White b Prabhakar 5
KA Wealleans lbw b Prabhakar 9
KR Rutherford c More b Razdan 30
GE Bradburn c More b Raju 42
M Douglas lbw b Raju 6
GR Larsen c Chandrasekhar b Hirwani 26
SA Thomson c Kapil Dev b Hirwani 4
+A Parore c Chandrasekhar b Hirwani 4
*MC Snedden b Hirwani 0
M Richardson c More b Prabhakar 18
J Millmow not out 16
Extras (b 7, lb 6) 13
Total (all out, 64.1 overs) 173
FoW: 1-23, 2-24, 3-74, 4-102, 5-103,
6-110, 7-126, 8-126, 9-141, 10-173.
Bowling O M R W
Kapil Dev 8 5 9 0
Prabhakar 12.1 4 24 3
Razdan 7 0 37 1
Raju 20 5 59 2
Hirwani 17 5 31 4