Mens round 1

Thiago Monteiro failed in the qualifying stages of US Open 2018 but the world #100 just managed to sneak into the main draw of this year's edition. His only previous main draw match in this tournament ended in a five-set defeat against Malek Jaziri in 2017.
The left-handed Brazilian heads into this clash with a 6/6 record on hardcourt this season with none of those six wins coming in the main draw on the main tour. He competed in only one tournament during the US Open series and failed in the first round against Alexei Popyrin in Winston Salem, despite winning the first set.
While Thiago Monteiro competed in the main draw of French Open and Wimbledon earlier this season, Bradley Klahn entered the main draw of the season's previous three slams, but neither of them could register a win.
Unlike the Brazilian, the big-serving American has won two main draw matches in the US Open so far in his career with both of those wins coming against a fellow lefty — Jurgen Melzer and Kenny de Schepper in the first round of 2012 and 2013 edition, respectively.
Both of these players would be delighted with the draw as they have got a very winnable match in the first round of a slam, despite being ranked around 100. Thiago Monteiro is the better all-round player, but ability on the hardcourt makes Bradley Klahn the favorite to win and level the H2H series (0-1, Aix en Provence challenger 2018).

After staying out of action for a couple of months, Tomas Berdych began his US Open preparation at Winston Salem last week where he defeated Andreas Seppi in three sets in the first round but failed in yet another three-set encounter against Filip Krajinovic, who later retired from his round of 16 clash in the following day.
The Czech's lack of fitness and confidence was clearly evident during his defeat against the Serbian as Tomas Berdych had an opportunity to serve for the match in the second set, but he squandered the chance and lost the deciding set 1-6.
Tomas Berdych, who shut down his 2018 season early at London due to injury, made his return earlier this season and delivered some encouraging results such as the runner-up finish at Doha and a semifinal appearance at Montpellier but his performance in the following months hasn't been good enough.
Surprisingly, US Open has been the former world #4 Tomas Berdych's least successful slam as he posted only two quarterfinal (or better) results in this tournament in 14 appearances. Despite ranked outside top 100, the Czech has got a bit fortunate with the draw, and he will be hoping to make good use of it by getting the job done against the qualifier.
Jenson Brooksby was handed a qualifying wildcard by the US Open, and he grabbed the opportunity by scoring solid wins over Kaichi Uchida, Yuichi Sugita and Pedro Martinez Portero earlier this week. On Monday, the teenager will make his first main draw appearance on the main tour this season.
The talented American was awarded a main draw wildcard by the US Open in 2018, but he went down quite cheaply against the eventual quarterfinalist John Millman in the first round, 4-6 2-6 0-6. However, Jenson Brooksby has gained some much-needed experience on tour since then and will be aiming to put up a better show this time around.
Tomas Berdych's ability and experience at this level makes him the deserved favorite in the pair's first-ever meeting, but his recent struggles should give Jenson Brooksby a lot of encouragement heading into the clash.