Daniel Brettig is an assistant editor at ESPNcricinfo. @danbrettig
Australia's No. 1 available batsman Usman Khawaja may be out of action for up to eight weeks, placing his availability for the home Test series against India in doubt, after he suffered a meniscal tear to his left knee that is likely to require surgery.
After twisting his left knee in warm-ups before day three of the Abu Dhabi Test against Pakistan, there were concerns that Khawaja had reinjured the anterior cruciate ligament that was reconstructed in 2014.
While overnight scans cleared Khawaja's ACL, the meniscal tear that was located will require a recovery time of anywhere from three to eight weeks, which is also dependent on whether surgery is required. Khawaja will consult a knee surgeon on his return home from the UAE. Already missing Steven Smith and David Warner due to suspension until April next year, the national team could ill-afford to lose Khawaja for any length of time, as their only remaining proven quantity as a Test batsman.
It remains uncertain whether Khawaja will bat in Australia's fourth innings of the Test, with his levels of knee function and pain to be monitored across the day. He did not take the field at all on day three after suffering the injury.
Following a seemingly innocuous incident in a fielding drill, he hobbled off the field for assessment and treatment, where he would remain throughout Pakistan's second innings. Initially it was thought Khawaja would only be off the field for a handful of overs, but ultimately he was absent all day, which meant he was ruled out of batting until No. 7 in the batting line-up, or until Australia had occupied the crease for the equivalent amount of time that he was missing from the field.
The seam bowler Peter Siddle said many of the squad were unaware that Khawaja had hurt his knee until they saw him unable to join them for the start of play. "Nah we didn't see it, some of the guys might've but I didn't, he hasn't really said too much," Siddle said. "Disappointing for him but he's getting a scan later tonight and they'll send it to the people who need to have a look at it in the next day or so and we'll find out more. At this stage that's all we know. Just fingers crossed for him, hopefully it comes back positive for him and he can get back out there.
"It was just something in warm-up, we were throwing the ball. So that's about all I know, I don't know what specifically happened, but something so small it's kept him out. So disappointing for him but fingers crossed he gets some good news tonight. Initially [he was] very flat, as anyone would know, knowing that he can't get out there with the boys and help out.
"But I think throughout the day he was up and about, moving around, helping us when we came in and trying to help us in the rooms. He's a positive guy, so fingers crossed for him and we get some good news tonight or tomorrow. Tonight once he's got the scan and we know more that'll determine from the doctor's point of view what he can and can't do. That's the big thing at the end of the day and just looking after his welfare. We'll see how that comes up tomorrow and we'll go from there."
In the wake of Khawaja's career-defining double of 85 and 141 to save Australia's blushes in Dubai, the gulf left when he cannot make runs was demonstrated when his early dismissal on the first evening here led to an inadequate first-innings tally of 145 that effectively surrendered any chance of victory in the match to Pakistan.
After Sarfraz Ahmed's team went on to set Australia a distant 538 to win in more than two days, the team coached by Justin Langer was left with a minimum of 192 overs to survive, with Khawaja's role in proceedings severely restricted. His was the second injury problem for the Australians in this match, after Mitchell Starc complained of hamstring tightness at the start of Pakistan's second innings having sustained a heavy workload in Dubai.
The effect on Starc's ability to cover the ground was confirmed by his placement at slip for much of the innings, while he was restricted to bowling a mere seven overs across two spells - four overs with the first new ball, three with the second. Siddle, so effective in the Big Bash League for the tournament-winning Adelaide Strikers last season, will be kept in the Twenty20 squad as cover.
After Dubai, amid the reverie of Australia's successful rearguard, Langer had commented on the physical and mental toll of Test matches, particularly those played in the UAE desert, where temperatures have routinely hovered near 40C with considerable humidity.
"I said to Travis Head actually when he missed out on the T20 side," Langer said. "At the end of this second Test you'll be coming and giving me a hug. "And Finchy said it to me today as well because Test cricket is so tiring. Physically and mentally, it's so draining. But that's all part of the back-to-back Test matches, especially with our young guys. We were going to have to recharge the batteries as well as we can and then have another crack at it. They're all important Test matches."
The other batsman expected to shoulder more responsibility while Smith and Warner are banned was Shaun Marsh, but a perfectly-pitched ball from Mir Hamza on the third evening completed a wretched series for the 35-year-old, tallying just 14 runs at 3.5 in four innings. Remarkably this is not Marsh's poorest series in Tests, after he managed just 17 at 2.83 against India in 2011-12. That run of outs was followed by an extended absence from the team, lasting until the 2014 tour of South Africa.
October 19, GMT 0530 The story was updated to include the findings of the scan on Khawaja's knee.