Liverpool captain Gerrard, who is injured and misses the Champions League clash with Lyon tonight (Wednesday), forged a good understanding with Alonso in midfield.
Alonso moved on to Real Madrid in the summer, since when Liverpool have struggled for form in the Premier League and Champions League.
Something missing: Gerrard admits the Reds have struggled without Alonso
It was a move which hit Gerrard hard.
'Devastated, yeah. Devastated. But there was nothing I could do about it,' he told FourFourTwo magazine. 'Xabi said a long time ago that he wanted another chapter in his career and finally he got it and his team-mates and the coaches couldn't stand in his way. We just have to say thanks and move forward without him.'
Real deal: Midfield maestro Alonso
Liverpool recouped around £30million for 27-year-old Alonso, and spent most of that on bringing replacement Alberto Aquilani to Anfield from Roma.
Aquilani missed the first two months of the season due to injury and Liverpool have already lost five Premier League matches.
Gerrard added: 'It's always going to be different when you lose one of the best players in the world - and people are finally realising that's what he is, on the back of his form for Real Madrid and the difference in us from last year.
'We've got other midfielders here doing a good job but it will take a while before Alonso's out of our system because he was such a top player.'
Rafa vows to walk tall through Lyon storm as Anfield anthem inspires Liverpool bossMARTIN SAMUEL: Liverpool boss Rafa Benitez has to be a Champions League Lyon tamerLiverpool limp in to Lyon with no defence for under-fire manager RafaTorres flies out as Rafa risks throwing injured Liverpool star into Lyons denJohn Arne Riise: Return to Liverpool? I'd rather stay at fourth-bottom RomaLIVERPOOL FC