Quins lead the Aviva Premiership by four points following eight wins out of eight, while they have also won two LV= Cup games and launched their European campaign with victory over Irish challengers Connacht last week.
But that impressive record goes on the line on Saturday when Brown and company tackle Heineken Cup rivals Gloucester at Kingsholm (kick-off 3.40pm) just six days after the west country club went within touching distance of toppling four-time European champions Toulouse.
"We have shown that we can win close games and that we can play a bit of rugby," said full-back Brown ahead of the Pool Six showdown.
"That is good for us, but we've got to keep going because teams really want to beat us now.
"We have learnt a lot from last season and from all the close games we had, and we've got pretty much the same squad this year.
"At the moment it is paying off for us, but we know we've got to keep working hard. If we get carried away with the unbeaten start, we will lose on Saturday."
Axed England centre Mike Tindall, who will appeal a £25,000 Rugby Football Union fine imposed for his off-field behaviour during the catastrophic World Cup campaign in New Zealand, spearheads Gloucester's victory bid in a Pool Six clash they must win to realistically keep alive quarter-final ambitions.
Tindall was Gloucester's best player during their four-point loss in Toulouse, and head coach Bryan Redpath retains 13 of that side, while calling up wing Lesley Vainikolo and hooker Scott Lawson.
"Being the Heineken, it's a little bit different, there is a bit of a buzz about it," Redpath said.
"They (Quins) have started the season really well, but we always have a massive incentive to do well at home. It's a great opportunity for us to show what we can do against a team bang in form."
Harlequins have made three changes to side that beat Connacht at the Stoop last week.
The rotation continues at hooker, with Joe Gray returning to start alongside Joe Marler and James Johnston, with Chris Brooker moving to the bench.
Argentinian Tomas Vallejos makes his first league start of the year since returning from the Rugby World Cup, replacing the injured Olly Kohn in the second row, while the back three remain unchanged.
There is only one change in the three-quarters, Matt Hopper makes his first competitive start for the club, replacing George Lowe who injured his ankle against Connacht.
The bench sees the return of Tim Fairbrother from injury and Charlie Matthews, while Danny Care continues his comeback, taking his place on the bench, alongside Rory Clegg and Tom Casson.
Gloucester: 15 Jonny May, 14 Charlie Sharples, 13 Henry Trinder, 12 Mike Tindall, 11 Lesley Vainikolo, 10 Freddie Burns, 9 Rory Lawson,8 Alasdair Strokosch. 7 Akapusi Qera, 6 Peter Buxton (c), 5 Jim Hamilton, 4 Will James, 3 Rupert Harden, 2 Scott Lawson, 1 Nick Wood.
Replacements: 16 Darren Dawidiuk, 17 Dan Murphy, 18 Dario Chistolini, 19 Tom Savage, 20 Luke Narraway, 21 Dave Lewis, 22 Tim Taylor, 23 Tom Voyce.
Harlequins: 15 Mike Brown, 14 Seb Stegmann, 13 Matt Hopper, 12 Jordan Turner-Hall, 11 Sam Smith, 10 Nick Evans, 9 Karl Dickson, 8 Nick Easter, 7 Chris Robshaw, 6 Maurie Faasavalu, 5 George Robson, 4 Tomas Vallejos, 3 James Johnston, 2 Joe Gray, 1 Joe Marler.
Replacements: 16 Chris Brooker, 17 Nic Mayhew, 18 Tim Fairbrother, 19 Charlie Matthews, 20 Luke Wallace, 21 Danny Care, 22 Rory Clegg, 23 Tom Casson.
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