Technically, the UEFA Champions League has been playing since late June, the beginning of qualifying for the champions of the continent's smallest countries. That said, it's the start of the group stage this week, not the qualifiers, that most fans think of as the real beginning of the European calendar.

For the rich, star-studded teams that are the favorites to advance out of the group stages, the hardest part of the Champions League isn't necessarily the European games themselves — it's the need to be competitive both in their domestic league and in Europe. Take Arsenal, which was drawn into a difficult Group F alongside Bayern Munich. On Nov. 4, a Wednesday, they head to Munich to take on the German champions, a tall order for any team in the world. The Saturday before, they travel to Swansea City, who can beat anyone in England; the Sunday following, they host crosstown rival Tottenham, annually one of the biggest and most contentious games.

To be successful in Europe requires constant navigation of stretches like that one, with big domestic games and marquee continental matchups piling up. In England, the deepest league on the continent, it's become nearly impossible to chase both league and European success; both Chelsea in 2012 and Liverpool in 2005 won the Champions League but finished outside the top four in England.

In Barcelona, the home of last year's champions, the questions are about depth. Barca was banned by UEFA from signing new players last January or over the summer because of violations of rules regarding signing under-18 players, and so it hasn't been able to strengthen its squad since mid-2014. Any team with Lionel Messi will always be the favorite against almost any other team, but the Catalan giants have their hands full in La Liga with Real Madrid and a retooled Atletico Madrid side. Real, which has made it at least to the Champions League semifinals five consecutive times, might be the European favorite this season.

European glory is why Bayern, with three consecutive German titles under its belts, still signed Douglas Costa and Arturo Vidal, two of the three most expensive signings in Germany this year. It's why Paris Saint-Germain, similarly the three-time defending French champion, spent big on Angel di Maria. Domestically, it's a case of the rich getting richer, but for the clubs, it's the challenge of building a team strong enough to compete with Real Madrid but also being able to coast in their own national league. For the big sides, choices must be made about priorities. The teams that get distracted domestically will have difficulty beating those that can focus on Europe.

SOCCER SHORT TAKES

Brian Stensaas — ASSOCIATED PRESS - AP, Star Tribune

• The United States' 4-1 loss to Brazil on Tuesday represented another low point for the men's national team, and more questions are being asked about Jurgen Klinsmann. The head coach started winger Alejandro Bedoya as a defensive midfielder, a position he'd never played as a pro, and it went badly enough that Klinsmann felt forced to substitute him off during the first half. The team's back line was torn apart by the Brazilians, as Klinsmann started yet another new, shaky center back partnership, with Michael Orozco alongside Ventura Alvarado — while two experienced center backs, Geoff Cameron and Tim Ream, played at fullback. All eyes are now on the team's Oct. 10 matchup with Mexico, with the winner advancing to the Confederations Cup. A U.S. victory would make the team's ugly summer a little prettier. A loss would leave many questioning Klinsmann's tenure, heading into the qualifiers for the 2018 World Cup.

• MLS Commissioner Don Garber suggested this week that his league's winner and the U.S. Open Cup winner could participate in a tournament with the Premier League champion and the winner of the FA Cup. A hundred details would have to be worked out for this to happen yearly, or even every four years, but if Garber can land the tournament, it'd be a major boon for his league — and for American fans.

• The NWSL playoffs begin Sunday on Fox Sports 1, with Kansas City visiting Chicago at 12:30 p.m. and Washington playing at Seattle at 8:30 p.m. The Seattle Reign, which beat Washington 2-1 last Saturday, will be heavily favored to again reach the championship game. Chicago, led by Christen Press' 10 goals in just 11 games, will also be favored, but less so. With the USA's upcoming games against Australia canceled because of a players' strike in Australia, Saturday might be among the most interesting days for women's soccer fans for the remainder of 2015.

• Minnesota native Kassey Kallman was one of just nine players to play every minute of the NWSL season. She started the entire year at center back for the Boston Breakers. Her team, though, finished in last place with just one win over the season's final three months.

WEEKEND WATCH GUIDE

Premier League: Manchester City at Crystal Palace, 9 a.m. Saturday, NBC Sports. Right now, it looks like nobody will ever score on Manchester City, never mind beat it; it has four consecutive wins and has outscored opponents 10-0. Crystal Palace, in second place in the standings, will look to derail City — but the London side hasn't been too good at home, where it has won just seven of its past 21 league matches.

La Liga: Barcelona at Atletico Madrid, 1:30 p.m. Saturday, beIN Sports. Barcelona is beginning a string that includes seven matches in 21 days, including away trips to Atletico and Sevilla and Champions League games with AS Roma and Bayer Leverkeusen. It's no small task for any squad, least of all a Barca team that was banned from bringing in any new players in 2015.

NASL: Carolina at Minnesota, 7 p.m. Saturday, Ch. 45. The RailHawks ended a four-match losing streak with a 2-0 win over Atlanta last week and a wild 3-3 draw with San Antonio in midweek, but they'll need a sustained run of wins if they hope to sneak back into the playoff picture. Minnesota, which knows well the trials and tribulations of playing while searching for a new owner, has won just one of its previous four home games against Carolina.

MLS: New England at Toronto, 4 p.m. Sunday, ESPN2. After a midseason swoon, New England has won five of six — and talisman Jermaine Jones is set to return from a sports hernia after playing for the United States in the country's two friendlies. Sebastian Giovinco, Toronto's leader, may return from an injury of his own. Which big-name midfielder will drive his team on to greater heights?