1. Tuesday's engrossing tie in the East Midlands confirmed one useful quality among many in this new United team: they play to the end.

It would not be exaggerating to say that many reporters at the iPro Stadium had their match reports drafted and polished as Derby headed towards a 1-0 win in the closing stages.

They - we - should not be so hasty again. Mike Jones' memorable equaliser with the final kick of normal time was a tribute to a side that refused to buckle.

It demonstrated persistence and guts, even after the substitution of Carlisle's best attacking player (Nicky Adams) had appeared to deprive them of some of their zest.

Coming a week after they rescued a point against Cheltenham in the 89th minute, it is no harm in establishing a reputation as a team that never quits.

League rivals will now know not to hit the snooze button when injury-time approaches against the Blues.

2. To go the distance with a Championship big beast three times - 90 minutes, extra-time and then the longest penalty shoot-out in League Cup history - requires strong levels of endurance.

United had that in abundance. There was a spell in the second half of extra-time, when Derby made one more attempt to settle the tie, that Carlisle demonstrated once more their powers of mental and physical concentration.

Tom Ince, one of many top names in the home ranks, made three attempts at cutting through United's box, with shots and dribbles. Each time, in fast succession, he was denied by the determined Macaulay Gillesphey.

Elsewhere, other players found impressive reserves, not least men like Tom Miller and Danny Grainger, who had ample work to do up and down their respective sides.

Whatever enviable facilities and techniques are available to a club as well-resourced as Derby, there must be greater credit to United's backroom team, including fitness coach Lee Fearn, for building this durability into Keith Curle's fourth-tier squad.

3. Nigel Pearson did not extend himself very far in the act of praising his former club after Tuesday's game. Searching for any compliments from the home boss was a rather futile act.

Each to their own. Pearson has his own matters to deal with at Derby, his own team to assess.

But was there nothing in the efforts of a club two levels and many millions beneath the Rams that was worthy of a public nod?

Of course there was. How about the 60-pass move that saw Carlisle work the ball patiently from man to man, early in the first half? How about the way they built decent attacks and restricted Derby to very little that was clear-cut for good periods?

How about their durability, as mentioned above? How about their guts at every stage? Their refusal to buckle when Championship pressure was applied?

It is fair, surely, to point these things out. Only an ostrich, perhaps, would ignore them.

4. Cup ties like this can be deceptive. Remember last season, when United took Liverpool all the way, and then flopped against a mediocre Newport side three days later?

Avoiding that is the challenge facing Curle's men now. It is no use showing up as well as they did at Derby and then being hustled to defeat at Barnet, back in the league.

At the iPro, United seemed to have good tactical versatility and players with the intelligence to adapt. For instance, Nicky Adams and Jamie Devitt excelled at dropping into central pockets or venturing wide as circumstances demanded it.

A fifth defender, last seen during the siege of Fratton Park, was also included from the start without any great discomfort, tactically.

In theory, then, United should be able to plan another effective and, if necessary, different strategy when they head to The Hive. No excuses if they get badly stung.

5. Anything Carlisle are able to achieve in the league this season will be closely linked to Nicky Adams' availability for as much of it as possible.

That was the strongest possible interpretation of Curle's surprising decision to substitute the former Northampton man after just 55 minutes on Tuesday.

"At the start of the second-half, I thought he [Adams] got a little bit lost in our shape," Curle later insisted. "He is a wide player and he likes to see the byline because he uses it as a guide."

Carlisle's manager can by all means be taken at face value. But it was very difficult not to view the decision differently, and think Curle was sparing his key man for more important contests up ahead.

Did the winger, after all, not cause havoc against Port Vale in the previous round by leaving his byline "guide", and drifting into central areas?

Yes; he is more adaptable than Curle's comment suggests - and one suspects the manager very much knows it.

6. If United are awarded penalties in the coming weeks and months, they shouldn't be short of candidates to take them.

Many of their kicks (and Derby's, in fairness) on Tuesday were almost German in quality.

Even two of those who were unsuccessful, Charlie Wyke and Joe McKee, still scored in the same marathon shoot-out. Only Jabo Ibehre didn't get a second chance to atone.

Otherwise, it was impressively deadly stuff, and among the many conversions it was good to see Danny Grainger and Luke Joyce willing, able and accurate after their disappointments at Liverpool last season.

Michael Raynes, too, deserves credit for holding his nerve during a delay whilst confusion over Bradley Johnson's involvement, or otherwise, was debated by the officials.

7. It has been notable, in recent weeks, that expectation around Carlisle's prospects has grown. How they acquitted themselves at Derby won't dampen such thoughts.

If the bookmakers are to be our guide, United's chances of success in League Two have increased because of their decent start to 2016/17.

They are today as short as 5/2 to be promoted, and will now be challenged with delivering on this; a pressure in itself.

United have yet to lose in League Two but have also only won one game from four. They are not yet a winning machine and certain habits still need to be acquired.

There is much to be optimistic about, as Tuesday confirmed - but now Curle's men have to get on with the serious business of ruthless delivery.