Dhoni says India won't take risks with Zaheer
He won that duel convincingly on the first morning, removing both Andrew Strauss and Alastair Cook in a classy spell before breaking down with a hamstring strain.
India went on to lose by 196 runs as the hosts made the most of Zaheer's absence from the attack, declaring in both innings.
With the next Test starting on Friday at Trent Bridge, the 32-year-old faces a race against time to be fit.
Dhoni admitted the loss of Zaheer was critical and does not intend to risk the same thing happening again in Nottingham.
"We have three days but I am not 100 per cent sure if we will play Zaheer or not," he said.
"We don't want to risk anyone if that only increases the chances of him getting injured further. It is very important to get the guys fully fit.
"After Zaheer was injured it was quite difficult in terms of resources but I felt the fast bowlers did a very good job - Praveen (Kumar] bowled really well in the first innings and Ishant (Sharma] bowled well in the second innings. Both of them bowled close to 60 overs each in the Test."
If Zaheer is ruled out, India must choose between back-up bowlers Sreesanth and Munaf Patel.
Coach Duncan Fletcher showed a clear preference for pace during his time in charge of England, suggesting the brisker - but more unpredictable - Sreesanth could get the nod.
India will also be hoping for an improved showing from their illustrious batting line-up as the series progresses.
Rahul Dravid scored a first-innings century at Lord's but the combined output from him, VVS Laxman and Sachin Tendulkar - who remains one away from an unprecedented hundredth international hundred - was well below expectations.
Dhoni blamed an uncertain batting order following an injury to Gautam Gambhir and Tendulkar's illness for the slump.
"Yes, we could have done with more partnerships from the top batsmen," he said.
"But it was tough for some of our batsmen because most of them were batting in different slots from their original number.
"Rahul opened, Sachin had to bat at a different number, Gautam batted at a different number. That also added pressure. Most of the things that could have gone wrong in the game really went wrong. It was tough for both the bowlers and the batsmen."