The UEFA Champions League semifinals kick off this week with four teams aiming for strong opening results in first-leg action.

Returning finalist Liverpool will face a tough test on Wednesday, traveling to the Camp Nou to take on Barcelona. Mohamed Salah and Lionel Messi headline the dangerous attacking units. Philippe Coutinho and Luis Suarez will suit up against their former side.

Elsewhere, Cinderella hopefuls Ajax face a trip to London to take on Tottenham. Led by the youth and talent of Frenkie de Jong and Matthijs de Ligt, Ajax will be seeking its first finals appearance since 1996, which it lost to Juventus. Tottenham has yet to make the UCL final in their history.

Here’s a closer look at this week’s Champions League action:

Barcelona vs. Liverpool (Wednesday, 3 p.m., EST. TNT)

Injuries to Note: Roberto Firmino will likely undergo a fitness test before the match, while Barcelona will be without Rafinha.

Key to the Match: Both sides have countless attacking weapons but will need to keep the other at bay. Gerard Pique and Virgil van Dijk headline each team’s backlines and will have to be strong in communicating with the rest of their defenders.

Players to Watch: Mo Salah will be tough for Barcelona to stop while Lionel Messi tries to carry the Catalan side into another final. Both players have skill, pace, and a knack for finding the back of the net. Expect both to see a lot of the ball.

Quote: “I think he is the best player in the world,” Virgil van Dijk said of Lionel Messi. “But you see how we play and how we defend. We don’t defend one v one, we defend all together and we attack all together as well so we will see. We will be ready.”

Tottenham vs. Ajax (Tuesday, 3 p.m., EST. TNT)

Injuries to Note: Harry Kane remains out for Tottenham while Harry Winks has a groin issue. Son Heung-Min is suspended for the first leg but Moussa Sissoko could feature after returning to training. Ajax have no major injury concerns.

Key to the Match: Ajax have been fearless as they’ve eliminated Real Madrid and Juventus in consecutive rounds. The Eredivisie side is well rested and should look to hit Tottenham early. Spurs will try to soak up pressure before springing on the counter with Lucas Moura and Christian Eriksen.

Players to Watch: With several starters out, Christian Eriksen will need to be influential for Tottenham. The Danish playmaker has the ability to score on his own while also setting up his teammates. Dusan Tadic is familiar with Spurs from his time at Southampton and has put in a sensational season for Ajax.

Quote: “Spurs are a great team with great players and we will have to be at the same level or better than we were against Real and Juventus in the last two rounds,” Ajax’s Donny van der Beek said.