A fierce playoff against one of South America’s top youth national teams awaits, and preparations for that will begin in earnest in a matter of days.

The U.S. Under-23 Men’s National Team and Colombia are set to meet in a two-legged playoff in three months, but some of the young Americans will spend time together in the senior U.S. side’s January camp in order to gain cohesion. It is currently unclear how many of the U.S. U-23 players head coach Jurgen Klinsmann will call in. Regardless, the group that is summoned will give Klinsmann and U-23 head coach Andreas Herzog a better idea of what kind of roster will be used come March when a spot in the summer Olympics is up for grabs.

The make-up of that squad for the games against Colombia will surely include many of the same faces that finished in third place in CONCACAF Olympic qualifying, but could also introduce some other players. John Brooks and Julian Green were included in the U-23’s last roster for friendlies back in November, and Herzog may want to count on their big-game experience and rhythm given that the MLS-based players will be in the infant stages of their season.

Brooks seems unlikely to be included, however. The Hertha Berlin centerback has been on a good run of form as of late, and stands a better chance of being called in by Klinsmann for March’s World Cup qualifiers vs. Guatemala. That would mean that the two of the likes of Matt Miazga, Cameron Carter-Vickers, Will Packwood and Shane O’Neill would have to be counted on in the center of the defense.

Behind them in goal, Ethan Horvath may have surpassed Cody Cropper as the No. 1 goalkeeper on the squad. Horvath closed out the 2015 Tippeligaen campaign as Molde’s starter, and that string of games combined with Cropper’s lack of first-team minutes at the club level both play out in the former’s favor. Jon Kempin and the younger and talented Zack Steffen serve as good options behind them, but only one can be the No. 3 goalkeeper.

Outside back seems to continue to be the area of weakness for this U.S. squad, but that could change if Desevio Payne is brought into the fold. Payne showed well at the Under-20 World Cup last summer, and may have been included in the Olympic qualifying roster this past fall if not for an untimely injury.

Eric Miller, Boyd Okwuono and Oscar Sorto are the other main candidates for the right back and left back spots, and impressive Chicago Fire rookie Matt Polser has enough versatility to provide extra cover.

Being able to play multiple positions could also win certain midfielders some roster spots. There is plenty of talent among that crop of players, and competition will be fierce as a result. The Foreign-based bunch would seem to have the edge given, again, that the MLS players will just be getting back to playing.

What that could translate into is more responsibility for Emerson Hyndman and Gedion Zelalem. Hyndman recently got his first start of the English Championship season for Fulham, and Zelalem has been a regular starter with Rangers in Scotland’s second division, so their spots on the roster seem as safe as any.

It is the midfield spots around them that are far less certain. Polster, Wil Trapp, Luis Gil and Fatai Alashe are MLS players who stand a good chance of being there come March, but at least one of them could be forced to miss out due to the roster size and the need for wide dynamic options like Green and Gboly Ariyibi. Kellyn Acosta should garner some consideration after his strong finish to the season with FC Dallas, and DeAndre Yedlin could also be an outside candidate if he’s left off Klinsmann’s March squad for World Cup qualifying.

Up top, Jordan Morris and Jerome Kiesewetter are locks so as long as they stay healthy. Morris — who is fresh off claiming a College Cup title — showed very well alongside Kiesewetter in Olympic qualifying and Herzog will surely not want to mess with that.

Which other forwards join them will come down to how Herzog wants to construct his squad. Alonso Hernandez, Maki Tall, and Khiry Shelton are candidates, but do not sleep on Rubio Rubin should he recover from his injury and get back to playing games for FC Utrecht.

In any case, Herzog has a sizable pool to choose from. Not everyone will be at their peak form come March given the different stages the players will be in during their respective seasons, but there is time between now and then to make a statement and potentially claim one of the coveted roster spots.