Pakistan ace pacer Shaheen is grappling with his pace and fitness and has failed to make a positive impression in all three games at the World Cup, where he has taken four wickets at a total cost of 139 runs.
"I don't know if there is a problem with his fitness," Waqar, who is in India as a commentator, told AFP.
"The missing link in his bowling is discipline and he is over trying to get wickets.
"When you do the same thing again and again like Shaheen is bowling to get his yorker going, then batsmen know that and they are ready for it."
Waqar suggested that Shaheen should emulate the example set by Bumrah, whom he described as a "top bowler."
The Indian spearhead is the joint top wicket-taker in the World Cup with eight wickets at just 11.52.
New Zealand spinner Mitchell Santner and fast bowler Matt Henry also have eight victims each.
India defeated Pakistan by seven wickets in Ahmedabad on Saturday, with Shaheen unable to assist Pakistan in defending a meagre 192-run target.
In contrast, Bumrah dismissed Mohammad Rizwan and Shadab Khan with two well-executed deliveries to finish with figures of 2-19 in seven overs.
"Bumrah is creating pressure and his line is top of the off stump. He bowled so well against Pakistan and created pressure to get wickets," said Waqar.
Shaheen, 23, has been leading Pakistan's new-ball attack since taking 16 wickets in five World Cup games in the United Kingdom four years ago.
Earlier, former Indian all-rounder Ravi Shastri strongly criticised the comparison of Shaheen to Wasim Akram during the Pakistan-India match, stating, "Shaheen is no Wasim Akram", claiming that the Pakistan star is "not special."
Waqar believes that the unavailability of his usual new-ball partner, Naseem Shah, who was sidelined from the World Cup due to a shoulder injury, may have had a negative effect on Shaheen's performances up to this juncture.
"Naseem is a good bowler and doesn't give many runs away," said Waqar of the 20-year-old.
"When Naseem creates pressure, batsmen take chances with other bowlers and they get wickets."
Waqar commented that Pakistan's bowling displayed a lack of discipline at the World Cup, with three matches resulting in two victories and one defeat.
"I don't think it's because of missing just one bowler, but it's because they are not keeping it simple."
Pakistan, who beat the Netherlands and Sri Lanka before losing to India, next face Australia in Bengaluru on Friday.
- Shaheen Afridi
