West Ham have won 12 of their 13 games in the competition this season, taking them to the brink of a first major trophy since the 1980 FA Cup.
Sevilla qualified for the semi-finals of the Europa League on Tuesday after Lucas Ocampos' late header broke Wolverhampton Wanderers' hearts, while Shakhtar Donetsk thumped Basel 4-1 to join the Spaniards in the last four.
Wolves battled into the quarter-finals of the Europa League on Thursday while Sevilla, Bayer Leverkusen and Basel enjoyed far more comfortable victories in the matches that brought the Europa League round of 16 to a belated close.
FC Basel will invest about 20 million euros ($22 million).
Ilkay Gundogan dazzled with two goals in Manchester City's 4-0 romp at FC Basel on Tuesday to leave the Premier League leaders on the verge of the Champions League quarter-finals.
Willian scored twice and won a pair of penalties as Chelsea thrashed 10-man Qarabag 4-0 in Baku to guarantee Antonio Conte's side a top-two finish in Group C.
Mohamed Elneny, an Egyptian international, joined Swiss club FC Basel in 2013 and has won the league title in each of his three seasons there.
Porto registered a comfortable 4-0 win against FC Basel to cruise through to the quarters.
Liverpool F.C. go to Switzerland having started their Group B campaign with a 2-1 win against Ludogorets Razgrad of Bulgaria earlier.
Real Madrid C.F. thumped five goals past Basel while Liverpool registered a 2-1 dramatic win against Ludogorets in Champions League.
Defeat against Atletico Madrid in La Liga has opened up the hidden scars of Real Madrid C.F..
Marcelo Diaz opened the scoring for the Swiss side in the 48th minute, capitalizing on an error by Steaua's Iasmin Latovlevici, who gave the ball to Marco Streller. The Basel forward passed to Diaz who unleashed a 20-meter shot past goalkeeper Ciprian Tartarusanu.
Arsenal, AC Milan, Schalke and Real Sociedad also join in the playoff round. Ten teams will advance from the playoff round and join 22 clubs which qualified directly for the group stage draw on Aug. 29.
It was a case of third time lucky for Chelsea, who lost in the semi-finals in both the League Cup and the FA Cup this season, while Basel fell short in their attempt to become the first Swiss team to reach a major European final.
The English Premier League outfit lead 2-1 from last week's semi-final, first leg in Switzerland and need only avoid defeat in west London to be assured of a place in the May 15 final in Amsterdam.
Although his side are well-placed to reach the final, Benitez says Chelsea must learn from the misfortunes that befell Tottenham Hotspur.